This file is indexed.

/usr/share/perl/5.14.2/pod/perlglossary.pod is in perl-doc 5.14.2-6ubuntu2.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
1742
1743
1744
1745
1746
1747
1748
1749
1750
1751
1752
1753
1754
1755
1756
1757
1758
1759
1760
1761
1762
1763
1764
1765
1766
1767
1768
1769
1770
1771
1772
1773
1774
1775
1776
1777
1778
1779
1780
1781
1782
1783
1784
1785
1786
1787
1788
1789
1790
1791
1792
1793
1794
1795
1796
1797
1798
1799
1800
1801
1802
1803
1804
1805
1806
1807
1808
1809
1810
1811
1812
1813
1814
1815
1816
1817
1818
1819
1820
1821
1822
1823
1824
1825
1826
1827
1828
1829
1830
1831
1832
1833
1834
1835
1836
1837
1838
1839
1840
1841
1842
1843
1844
1845
1846
1847
1848
1849
1850
1851
1852
1853
1854
1855
1856
1857
1858
1859
1860
1861
1862
1863
1864
1865
1866
1867
1868
1869
1870
1871
1872
1873
1874
1875
1876
1877
1878
1879
1880
1881
1882
1883
1884
1885
1886
1887
1888
1889
1890
1891
1892
1893
1894
1895
1896
1897
1898
1899
1900
1901
1902
1903
1904
1905
1906
1907
1908
1909
1910
1911
1912
1913
1914
1915
1916
1917
1918
1919
1920
1921
1922
1923
1924
1925
1926
1927
1928
1929
1930
1931
1932
1933
1934
1935
1936
1937
1938
1939
1940
1941
1942
1943
1944
1945
1946
1947
1948
1949
1950
1951
1952
1953
1954
1955
1956
1957
1958
1959
1960
1961
1962
1963
1964
1965
1966
1967
1968
1969
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2019
2020
2021
2022
2023
2024
2025
2026
2027
2028
2029
2030
2031
2032
2033
2034
2035
2036
2037
2038
2039
2040
2041
2042
2043
2044
2045
2046
2047
2048
2049
2050
2051
2052
2053
2054
2055
2056
2057
2058
2059
2060
2061
2062
2063
2064
2065
2066
2067
2068
2069
2070
2071
2072
2073
2074
2075
2076
2077
2078
2079
2080
2081
2082
2083
2084
2085
2086
2087
2088
2089
2090
2091
2092
2093
2094
2095
2096
2097
2098
2099
2100
2101
2102
2103
2104
2105
2106
2107
2108
2109
2110
2111
2112
2113
2114
2115
2116
2117
2118
2119
2120
2121
2122
2123
2124
2125
2126
2127
2128
2129
2130
2131
2132
2133
2134
2135
2136
2137
2138
2139
2140
2141
2142
2143
2144
2145
2146
2147
2148
2149
2150
2151
2152
2153
2154
2155
2156
2157
2158
2159
2160
2161
2162
2163
2164
2165
2166
2167
2168
2169
2170
2171
2172
2173
2174
2175
2176
2177
2178
2179
2180
2181
2182
2183
2184
2185
2186
2187
2188
2189
2190
2191
2192
2193
2194
2195
2196
2197
2198
2199
2200
2201
2202
2203
2204
2205
2206
2207
2208
2209
2210
2211
2212
2213
2214
2215
2216
2217
2218
2219
2220
2221
2222
2223
2224
2225
2226
2227
2228
2229
2230
2231
2232
2233
2234
2235
2236
2237
2238
2239
2240
2241
2242
2243
2244
2245
2246
2247
2248
2249
2250
2251
2252
2253
2254
2255
2256
2257
2258
2259
2260
2261
2262
2263
2264
2265
2266
2267
2268
2269
2270
2271
2272
2273
2274
2275
2276
2277
2278
2279
2280
2281
2282
2283
2284
2285
2286
2287
2288
2289
2290
2291
2292
2293
2294
2295
2296
2297
2298
2299
2300
2301
2302
2303
2304
2305
2306
2307
2308
2309
2310
2311
2312
2313
2314
2315
2316
2317
2318
2319
2320
2321
2322
2323
2324
2325
2326
2327
2328
2329
2330
2331
2332
2333
2334
2335
2336
2337
2338
2339
2340
2341
2342
2343
2344
2345
2346
2347
2348
2349
2350
2351
2352
2353
2354
2355
2356
2357
2358
2359
2360
2361
2362
2363
2364
2365
2366
2367
2368
2369
2370
2371
2372
2373
2374
2375
2376
2377
2378
2379
2380
2381
2382
2383
2384
2385
2386
2387
2388
2389
2390
2391
2392
2393
2394
2395
2396
2397
2398
2399
2400
2401
2402
2403
2404
2405
2406
2407
2408
2409
2410
2411
2412
2413
2414
2415
2416
2417
2418
2419
2420
2421
2422
2423
2424
2425
2426
2427
2428
2429
2430
2431
2432
2433
2434
2435
2436
2437
2438
2439
2440
2441
2442
2443
2444
2445
2446
2447
2448
2449
2450
2451
2452
2453
2454
2455
2456
2457
2458
2459
2460
2461
2462
2463
2464
2465
2466
2467
2468
2469
2470
2471
2472
2473
2474
2475
2476
2477
2478
2479
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
2521
2522
2523
2524
2525
2526
2527
2528
2529
2530
2531
2532
2533
2534
2535
2536
2537
2538
2539
2540
2541
2542
2543
2544
2545
2546
2547
2548
2549
2550
2551
2552
2553
2554
2555
2556
2557
2558
2559
2560
2561
2562
2563
2564
2565
2566
2567
2568
2569
2570
2571
2572
2573
2574
2575
2576
2577
2578
2579
2580
2581
2582
2583
2584
2585
2586
2587
2588
2589
2590
2591
2592
2593
2594
2595
2596
2597
2598
2599
2600
2601
2602
2603
2604
2605
2606
2607
2608
2609
2610
2611
2612
2613
2614
2615
2616
2617
2618
2619
2620
2621
2622
2623
2624
2625
2626
2627
2628
2629
2630
2631
2632
2633
2634
2635
2636
2637
2638
2639
2640
2641
2642
2643
2644
2645
2646
2647
2648
2649
2650
2651
2652
2653
2654
2655
2656
2657
2658
2659
2660
2661
2662
2663
2664
2665
2666
2667
2668
2669
2670
2671
2672
2673
2674
2675
2676
2677
2678
2679
2680
2681
2682
2683
2684
2685
2686
2687
2688
2689
2690
2691
2692
2693
2694
2695
2696
2697
2698
2699
2700
2701
2702
2703
2704
2705
2706
2707
2708
2709
2710
2711
2712
2713
2714
2715
2716
2717
2718
2719
2720
2721
2722
2723
2724
2725
2726
2727
2728
2729
2730
2731
2732
2733
2734
2735
2736
2737
2738
2739
2740
2741
2742
2743
2744
2745
2746
2747
2748
2749
2750
2751
2752
2753
2754
2755
2756
2757
2758
2759
2760
2761
2762
2763
2764
2765
2766
2767
2768
2769
2770
2771
2772
2773
2774
2775
2776
2777
2778
2779
2780
2781
2782
2783
2784
2785
2786
2787
2788
2789
2790
2791
2792
2793
2794
2795
2796
2797
2798
2799
2800
2801
2802
2803
2804
2805
2806
2807
2808
2809
2810
2811
2812
2813
2814
2815
2816
2817
2818
2819
2820
2821
2822
2823
2824
2825
2826
2827
2828
2829
2830
2831
2832
2833
2834
2835
2836
2837
2838
2839
2840
2841
2842
2843
2844
2845
2846
2847
2848
2849
2850
2851
2852
2853
2854
2855
2856
2857
2858
2859
2860
2861
2862
2863
2864
2865
2866
2867
2868
2869
2870
2871
2872
2873
2874
2875
2876
2877
2878
2879
2880
2881
2882
2883
2884
2885
2886
2887
2888
2889
2890
2891
2892
2893
2894
2895
2896
2897
2898
2899
2900
2901
2902
2903
2904
2905
2906
2907
2908
2909
2910
2911
2912
2913
2914
2915
2916
2917
2918
2919
2920
2921
2922
2923
2924
2925
2926
2927
2928
2929
2930
2931
2932
2933
2934
2935
2936
2937
2938
2939
2940
2941
2942
2943
2944
2945
2946
2947
2948
2949
2950
2951
2952
2953
2954
2955
2956
2957
2958
2959
2960
2961
2962
2963
2964
2965
2966
2967
2968
2969
2970
2971
2972
2973
2974
2975
2976
2977
2978
2979
2980
2981
2982
2983
2984
2985
2986
2987
2988
2989
2990
2991
2992
2993
2994
2995
2996
2997
2998
2999
3000
3001
3002
3003
3004
3005
3006
3007
3008
3009
3010
3011
3012
3013
3014
3015
3016
3017
3018
3019
3020
3021
3022
3023
3024
3025
3026
3027
3028
3029
3030
3031
3032
3033
3034
3035
3036
3037
3038
3039
3040
3041
3042
3043
3044
3045
3046
3047
3048
3049
3050
3051
3052
3053
3054
3055
3056
3057
3058
3059
3060
3061
3062
3063
3064
3065
3066
3067
3068
3069
3070
3071
3072
3073
3074
3075
3076
3077
3078
3079
3080
3081
3082
3083
3084
3085
3086
3087
3088
3089
3090
3091
3092
3093
3094
3095
3096
3097
3098
3099
3100
3101
3102
3103
3104
3105
3106
3107
3108
3109
3110
3111
3112
3113
3114
3115
3116
3117
3118
3119
3120
3121
3122
3123
3124
3125
3126
3127
3128
3129
3130
3131
3132
3133
3134
3135
3136
3137
3138
3139
3140
3141
3142
3143
3144
3145
3146
3147
3148
3149
3150
3151
3152
3153
3154
3155
3156
3157
3158
3159
3160
3161
3162
3163
3164
3165
3166
3167
3168
3169
3170
3171
3172
3173
3174
3175
3176
3177
3178
3179
3180
3181
3182
3183
3184
3185
3186
3187
3188
3189
3190
3191
3192
3193
3194
3195
3196
3197
3198
3199
3200
3201
3202
3203
3204
3205
3206
3207
3208
3209
3210
3211
3212
3213
3214
3215
3216
3217
3218
3219
3220
3221
3222
3223
3224
3225
3226
3227
3228
3229
3230
3231
3232
3233
3234
3235
3236
3237
3238
3239
3240
3241
3242
3243
3244
3245
3246
3247
3248
3249
3250
3251
3252
3253
3254
3255
3256
3257
3258
3259
3260
3261
3262
3263
3264
3265
3266
3267
3268
3269
3270
3271
3272
3273
3274
3275
3276
3277
3278
3279
3280
3281
3282
3283
3284
3285
3286
3287
3288
3289
3290
3291
3292
3293
3294
3295
3296
3297
3298
3299
3300
3301
3302
3303
3304
3305
3306
3307
3308
3309
3310
3311
3312
3313
3314
3315
3316
3317
3318
3319
3320
3321
3322
3323
3324
3325
3326
3327
3328
3329
3330
3331
3332
3333
3334
3335
3336
3337
3338
3339
3340
3341
3342
3343
3344
3345
3346
3347
3348
3349
3350
3351
3352
3353
3354
3355
3356
3357
3358
3359
3360
3361
3362
3363
3364
3365
3366
3367
3368
3369
3370
3371
3372
3373
3374
3375
3376
3377
3378
3379
3380
3381
3382
3383
3384
3385
3386
3387
3388
3389
3390
3391
3392
3393
3394
3395
3396
3397
3398
3399
3400
3401
3402
3403
3404
3405
3406
3407
3408
3409
3410
3411
3412
3413
3414
3415
3416
3417
3418
3419
3420
3421
3422
3423
3424
3425
3426
3427
3428
3429
3430
=head1 NAME

perlglossary - Perl Glossary

=head1 DESCRIPTION

A glossary of terms (technical and otherwise) used in the Perl documentation.
Other useful sources include the Free On-Line Dictionary of Computing
L<http://foldoc.doc.ic.ac.uk/foldoc/index.html>, the Jargon File
L<http://catb.org/~esr/jargon/>, and Wikipedia L<http://www.wikipedia.org/>.

=head2 A

=over 4

=item accessor methods

A L</method> used to indirectly inspect or update an L</object>'s
state (its L<instance variables|/instance variable>).

=item actual arguments

The L<scalar values|/scalar value> that you supply to a L</function>
or L</subroutine> when you call it.  For instance, when you call
C<power("puff")>, the string C<"puff"> is the actual argument.  See
also L</argument> and L</formal arguments>.

=item address operator

Some languages work directly with the memory addresses of values, but
this can be like playing with fire.  Perl provides a set of asbestos
gloves for handling all memory management.  The closest to an address
operator in Perl is the backslash operator, but it gives you a L</hard
reference>, which is much safer than a memory address.

=item algorithm

A well-defined sequence of steps, clearly enough explained that even a
computer could do them.

=item alias

A nickname for something, which behaves in all ways as though you'd
used the original name instead of the nickname.  Temporary aliases are
implicitly created in the loop variable for C<foreach> loops, in the
C<$_> variable for L<map|perlfunc/map> or L<grep|perlfunc/grep>
operators, in C<$a> and C<$b> during L<sort|perlfunc/sort>'s
comparison function, and in each element of C<@_> for the L</actual
arguments> of a subroutine call.  Permanent aliases are explicitly
created in L<packages|/package> by L<importing|/import> symbols or by
assignment to L<typeglobs|/typeglob>.  Lexically scoped aliases for
package variables are explicitly created by the L<our|perlfunc/our>
declaration.

=item alternatives

A list of possible choices from which you may select only one, as in
"Would you like door A, B, or C?"  Alternatives in regular expressions
are separated with a single vertical bar: C<|>.  Alternatives in
normal Perl expressions are separated with a double vertical bar:
C<||>.  Logical alternatives in L</Boolean> expressions are separated
with either C<||> or C<or>.

=item anonymous

Used to describe a L</referent> that is not directly accessible
through a named L</variable>.  Such a referent must be indirectly
accessible through at least one L</hard reference>.  When the last
hard reference goes away, the anonymous referent is destroyed without
pity.

=item architecture

The kind of computer you're working on, where one "kind" of computer
means all those computers sharing a compatible machine language.
Since Perl programs are (typically) simple text files, not executable
images, a Perl program is much less sensitive to the architecture it's
running on than programs in other languages, such as C, that are
compiled into machine code.  See also L</platform> and L</operating
system>.

=item argument

A piece of data supplied to a L<program|/executable file>,
L</subroutine>, L</function>, or L</method> to tell it what it's
supposed to do.  Also called a "parameter".

=item ARGV

The name of the array containing the L</argument> L</vector> from the
command line.  If you use the empty C<< E<lt>E<gt> >> operator, L</ARGV> is
the name of both the L</filehandle> used to traverse the arguments and
the L</scalar> containing the name of the current input file.

=item arithmetical operator

A L</symbol> such as C<+> or C</> that tells Perl to do the arithmetic
you were supposed to learn in grade school.

=item array

An ordered sequence of L<values|/value>, stored such that you can
easily access any of the values using an integer L</subscript>
that specifies the value's L</offset> in the sequence.

=item array context

An archaic expression for what is more correctly referred to as
L</list context>.

=item ASCII

The American Standard Code for Information Interchange (a 7-bit
character set adequate only for poorly representing English text).
Often used loosely to describe the lowest 128 values of the various
ISO-8859-X character sets, a bunch of mutually incompatible 8-bit
codes sometimes described as half ASCII.  See also L</Unicode>.

=item assertion

A component of a L</regular expression> that must be true for the
pattern to match but does not necessarily match any characters itself.
Often used specifically to mean a L</zero width> assertion.

=item assignment

An L</operator> whose assigned mission in life is to change the value
of a L</variable>.

=item assignment operator

Either a regular L</assignment>, or a compound L</operator> composed
of an ordinary assignment and some other operator, that changes the
value of a variable in place, that is, relative to its old value.  For
example, C<$a += 2> adds C<2> to C<$a>.

=item associative array

See L</hash>.  Please.

=item associativity

Determines whether you do the left L</operator> first or the right
L</operator> first when you have "A L</operator> B L</operator> C" and
the two operators are of the same precedence.  Operators like C<+> are
left associative, while operators like C<**> are right associative.
See L<perlop> for a list of operators and their associativity.

=item asynchronous

Said of events or activities whose relative temporal ordering is
indeterminate because too many things are going on at once.  Hence, an
asynchronous event is one you didn't know when to expect.

=item atom

A L</regular expression> component potentially matching a
L</substring> containing one or more characters and treated as an
indivisible syntactic unit by any following L</quantifier>.  (Contrast
with an L</assertion> that matches something of L</zero width> and may
not be quantified.)

=item atomic operation

When Democritus gave the word "atom" to the indivisible bits of
matter, he meant literally something that could not be cut: I<a->
(not) + I<tomos> (cuttable).  An atomic operation is an action that
can't be interrupted, not one forbidden in a nuclear-free zone.

=item attribute

A new feature that allows the declaration of L<variables|/variable>
and L<subroutines|/subroutine> with modifiers as in C<sub foo : locked
method>.  Also, another name for an L</instance variable> of an
L</object>.

=item autogeneration

A feature of L</operator overloading> of L<objects|/object>, whereby
the behavior of certain L<operators|/operator> can be reasonably
deduced using more fundamental operators.  This assumes that the
overloaded operators will often have the same relationships as the
regular operators.  See L<perlop>.

=item autoincrement

To add one to something automatically, hence the name of the C<++>
operator.  To instead subtract one from something automatically is
known as an "autodecrement".

=item autoload

To load on demand.  (Also called "lazy" loading.)  Specifically, to
call an L<AUTOLOAD|perlsub/Autoloading> subroutine on behalf of an
undefined subroutine.

=item autosplit

To split a string automatically, as the B<-a> L</switch> does when
running under B<-p> or B<-n> in order to emulate L</awk>.  (See also
the L<AutoSplit> module, which has nothing to do with the B<-a>
switch, but a lot to do with autoloading.)

=item autovivification

A Greco-Roman word meaning "to bring oneself to life".  In Perl,
storage locations (L<lvalues|/lvalue>) spontaneously generate
themselves as needed, including the creation of any L</hard reference>
values to point to the next level of storage.  The assignment
C<$a[5][5][5][5][5] = "quintet"> potentially creates five scalar
storage locations, plus four references (in the first four scalar
locations) pointing to four new anonymous arrays (to hold the last
four scalar locations).  But the point of autovivification is that you
don't have to worry about it.

=item AV

Short for "array value", which refers to one of Perl's internal data
types that holds an L</array>.  The L</AV> type is a subclass of
L</SV>.

=item awk

Descriptive editing term--short for "awkward".  Also coincidentally
refers to a venerable text-processing language from which Perl derived
some of its high-level ideas.

=back

=head2 B

=over 4

=item backreference

A substring L<captured|/capturing> by a subpattern within
unadorned parentheses in a L</regex>, also referred to as a capture group.  The
sequences (C<\g1>, C<\g2>, etc.)  later in the same pattern refer back to
the corresponding subpattern in the current match.  Outside the pattern,
the numbered variables (C<$1>, C<$2>, etc.) continue to refer to these
same values, as long as the pattern was the last successful match of
the current dynamic scope.  C<\g{-1}> can be used to refer to a group by
relative rather than absolute position; and groups can be also be named, and
referred to later by name rather than number.  See L<perlre/"Capture groups">.

=item backtracking

The practice of saying, "If I had to do it all over, I'd do it
differently," and then actually going back and doing it all over
differently.  Mathematically speaking, it's returning from an
unsuccessful recursion on a tree of possibilities.  Perl backtracks
when it attempts to match patterns with a L</regular expression>, and
its earlier attempts don't pan out.  See L<perlre/Backtracking>.

=item backward compatibility

Means you can still run your old program because we didn't break any
of the features or bugs it was relying on.

=item bareword

A word sufficiently ambiguous to be deemed illegal under L<use strict
'subs'|strict/strict subs>.  In the absence of that stricture, a
bareword is treated as if quotes were around it.

=item base class

A generic L</object> type; that is, a L</class> from which other, more
specific classes are derived genetically by L</inheritance>.  Also
called a "superclass" by people who respect their ancestors.

=item big-endian

From Swift: someone who eats eggs big end first.  Also used of
computers that store the most significant L</byte> of a word at a
lower byte address than the least significant byte.  Often considered
superior to little-endian machines.  See also L</little-endian>.

=item binary

Having to do with numbers represented in base 2.  That means there's
basically two numbers, 0 and 1.  Also used to describe a "non-text
file", presumably because such a file makes full use of all the binary
bits in its bytes.  With the advent of L</Unicode>, this distinction,
already suspect, loses even more of its meaning.

=item binary operator

An L</operator> that takes two L<operands|/operand>.

=item bind

To assign a specific L</network address> to a L</socket>.

=item bit

An integer in the range from 0 to 1, inclusive.  The smallest possible
unit of information storage.  An eighth of a L</byte> or of a dollar.
(The term "Pieces of Eight" comes from being able to split the old
Spanish dollar into 8 bits, each of which still counted for money.
That's why a 25-cent piece today is still "two bits".)

=item bit shift

The movement of bits left or right in a computer word, which has the
effect of multiplying or dividing by a power of 2.

=item bit string

A sequence of L<bits|/bit> that is actually being thought of as a
sequence of bits, for once.

=item bless

In corporate life, to grant official approval to a thing, as in, "The
VP of Engineering has blessed our WebCruncher project." Similarly in
Perl, to grant official approval to a L</referent> so that it can
function as an L</object>, such as a WebCruncher object.  See
L<perlfunc/"bless">.

=item block

What a L</process> does when it has to wait for something: "My process
blocked waiting for the disk."  As an unrelated noun, it refers to a
large chunk of data, of a size that the L</operating system> likes to
deal with (normally a power of two such as 512 or 8192).  Typically
refers to a chunk of data that's coming from or going to a disk file.

=item BLOCK

A syntactic construct consisting of a sequence of Perl
L<statements|/statement> that is delimited by braces.  The C<if> and
C<while> statements are defined in terms of L<BLOCKs|/BLOCK>, for instance.
Sometimes we also say "block" to mean a lexical scope; that is, a
sequence of statements that act like a L</BLOCK>, such as within an
L<eval|perlfunc/eval> or a file, even though the statements aren't
delimited by braces.

=item block buffering

A method of making input and output efficient by passing one L</block>
at a time.  By default, Perl does block buffering to disk files.  See
L</buffer> and L</command buffering>.

=item Boolean

A value that is either L</true> or L</false>.

=item Boolean context

A special kind of L</scalar context> used in conditionals to decide
whether the L</scalar value> returned by an expression is L</true> or
L</false>.  Does not evaluate as either a string or a number.  See
L</context>.

=item breakpoint

A spot in your program where you've told the debugger to stop
L<execution|/execute> so you can poke around and see whether anything
is wrong yet.

=item broadcast

To send a L</datagram> to multiple destinations simultaneously.

=item BSD

A psychoactive drug, popular in the 80s, probably developed at
U. C. Berkeley or thereabouts.  Similar in many ways to the
prescription-only medication called "System V", but infinitely more
useful.  (Or, at least, more fun.)  The full chemical name is
"Berkeley Standard Distribution".

=item bucket

A location in a L</hash table> containing (potentially) multiple
entries whose keys "hash" to the same hash value according to its hash
function.  (As internal policy, you don't have to worry about it,
unless you're into internals, or policy.)

=item buffer

A temporary holding location for data.  L<Block buffering|/block
buffering> means that the data is passed on to its destination
whenever the buffer is full.  L<Line buffering|/line buffering> means
that it's passed on whenever a complete line is received.  L<Command
buffering|/command buffering> means that it's passed every time you do
a L<print|perlfunc/print> command (or equivalent).  If your output is
unbuffered, the system processes it one byte at a time without the use
of a holding area.  This can be rather inefficient.

=item built-in

A L</function> that is predefined in the language.  Even when hidden
by L</overriding>, you can always get at a built-in function by
L<qualifying|/qualified> its name with the C<CORE::> pseudo-package.

=item bundle

A group of related modules on L</CPAN>.  (Also, sometimes refers to a
group of command-line switches grouped into one L</switch cluster>.)

=item byte

A piece of data worth eight L<bits|/bit> in most places.

=item bytecode

A pidgin-like language spoken among 'droids when they don't wish to
reveal their orientation (see L</endian>).  Named after some similar
languages spoken (for similar reasons) between compilers and
interpreters in the late 20th century.  These languages are
characterized by representing everything as a
non-architecture-dependent sequence of bytes.

=back

=head2 C

=over 4

=item C

A language beloved by many for its inside-out L</type> definitions,
inscrutable L</precedence> rules, and heavy L</overloading> of the
function-call mechanism.  (Well, actually, people first switched to C
because they found lowercase identifiers easier to read than upper.)
Perl is written in C, so it's not surprising that Perl borrowed a few
ideas from it.

=item C preprocessor

The typical C compiler's first pass, which processes lines beginning
with C<#> for conditional compilation and macro definition and does
various manipulations of the program text based on the current
definitions.  Also known as I<cpp>(1).

=item call by reference

An L</argument>-passing mechanism in which the L</formal arguments>
refer directly to the L</actual arguments>, and the L</subroutine> can
change the actual arguments by changing the formal arguments.  That
is, the formal argument is an L</alias> for the actual argument.  See
also L</call by value>.

=item call by value

An L</argument>-passing mechanism in which the L</formal arguments>
refer to a copy of the L</actual arguments>, and the L</subroutine>
cannot change the actual arguments by changing the formal arguments.
See also L</call by reference>.

=item callback

A L</handler> that you register with some other part of your program
in the hope that the other part of your program will L</trigger> your
handler when some event of interest transpires.

=item canonical

Reduced to a standard form to facilitate comparison.

=item capture buffer, capture group

These two terms are synonymous:
a L<captured substring|/capturing> by a regex subpattern.

=item capturing

The use of parentheses around a L</subpattern> in a L</regular
expression> to store the matched L</substring> as a L</backreference>
or L<capture group|/capture buffer, capture group>.
(Captured strings are also returned as a list in L</list context>.)

=item character

A small integer representative of a unit of orthography.
Historically, characters were usually stored as fixed-width integers
(typically in a byte, or maybe two, depending on the character set),
but with the advent of UTF-8, characters are often stored in a
variable number of bytes depending on the size of the integer that
represents the character.  Perl manages this transparently for you,
for the most part.

=item character class

A square-bracketed list of characters used in a L</regular expression>
to indicate that any character of the set may occur at a given point.
Loosely, any predefined set of characters so used.

=item character property

A predefined L</character class> matchable by the C<\p>
L</metasymbol>.  Many standard properties are defined for L</Unicode>.

=item circumfix operator

An L</operator> that surrounds its L</operand>, like the angle
operator, or parentheses, or a hug.

=item class

A user-defined L</type>, implemented in Perl via a L</package> that
provides (either directly or by inheritance) L<methods|/method> (that
is, L<subroutines|/subroutine>) to handle L<instances|/instance> of
the class (its L<objects|/object>).  See also L</inheritance>.

=item class method

A L</method> whose L</invocant> is a L</package> name, not an
L</object> reference.  A method associated with the class as a whole.

=item client

In networking, a L</process> that initiates contact with a L</server>
process in order to exchange data and perhaps receive a service.

=item cloister

A L</cluster> used to restrict the scope of a L</regular expression
modifier>.

=item closure

An L</anonymous> subroutine that, when a reference to it is generated
at run time, keeps track of the identities of externally visible
L<lexical variables|/lexical variable> even after those lexical
variables have supposedly gone out of L</scope>.  They're called
"closures" because this sort of behavior gives mathematicians a sense
of closure.

=item cluster

A parenthesized L</subpattern> used to group parts of a L</regular
expression> into a single L</atom>.

=item CODE

The word returned by the L<ref|perlfunc/ref> function when you apply
it to a reference to a subroutine.  See also L</CV>.

=item code generator

A system that writes code for you in a low-level language, such as
code to implement the backend of a compiler.  See L</program
generator>.

=item code point

The position of a character in a character set encoding.  The character
C<NULL> is almost certainly at the zeroth position in all character
sets, so its code point is 0.  The code point for the C<SPACE>
character in the ASCII character set is 0x20, or 32 decimal; in EBCDIC
it is 0x40, or 64 decimal.  The L<ord|perlfunc/ord> function returns
the code point of a character.

"code position" and "ordinal" mean the same thing as "code point".

=item code subpattern

A L</regular expression> subpattern whose real purpose is to execute
some Perl code, for example, the C<(?{...})> and C<(??{...})>
subpatterns.

=item collating sequence

The order into which L<characters|/character> sort.  This is used by
L</string> comparison routines to decide, for example, where in this
glossary to put "collating sequence".

=item command

In L</shell> programming, the syntactic combination of a program name
and its arguments.  More loosely, anything you type to a shell (a
command interpreter) that starts it doing something.  Even more
loosely, a Perl L</statement>, which might start with a L</label> and
typically ends with a semicolon.

=item command buffering

A mechanism in Perl that lets you store up the output of each Perl
L</command> and then flush it out as a single request to the
L</operating system>.  It's enabled by setting the C<$|>
(C<$AUTOFLUSH>) variable to a true value.  It's used when you don't
want data sitting around not going where it's supposed to, which may
happen because the default on a L</file> or L</pipe> is to use
L</block buffering>.

=item command name

The name of the program currently executing, as typed on the command
line.  In C, the L</command> name is passed to the program as the
first command-line argument.  In Perl, it comes in separately as
C<$0>.

=item command-line arguments

The L<values|/value> you supply along with a program name when you
tell a L</shell> to execute a L</command>.  These values are passed to
a Perl program through C<@ARGV>.

=item comment

A remark that doesn't affect the meaning of the program.  In Perl, a
comment is introduced by a C<#> character and continues to the end of
the line.

=item compilation unit

The L</file> (or L</string>, in the case of L<eval|perlfunc/eval>)
that is currently being compiled.

=item compile phase

Any time before Perl starts running your main program.  See also
L</run phase>.  Compile phase is mostly spent in L</compile time>, but
may also be spent in L</run time> when C<BEGIN> blocks,
L<use|perlfunc/use> declarations, or constant subexpressions are being
evaluated.  The startup and import code of any L<use|perlfunc/use>
declaration is also run during compile phase.

=item compile time

The time when Perl is trying to make sense of your code, as opposed to
when it thinks it knows what your code means and is merely trying to
do what it thinks your code says to do, which is L</run time>.

=item compiler

Strictly speaking, a program that munches up another program and spits
out yet another file containing the program in a "more executable"
form, typically containing native machine instructions.  The I<perl>
program is not a compiler by this definition, but it does contain a
kind of compiler that takes a program and turns it into a more
executable form (L<syntax trees|/syntax tree>) within the I<perl>
process itself, which the L</interpreter> then interprets.  There are,
however, extension L<modules|/module> to get Perl to act more like a
"real" compiler.  See L<O>.

=item composer

A "constructor" for a L</referent> that isn't really an L</object>,
like an anonymous array or a hash (or a sonata, for that matter).  For
example, a pair of braces acts as a composer for a hash, and a pair of
brackets acts as a composer for an array.  See L<perlref/Making
References>.

=item concatenation

The process of gluing one cat's nose to another cat's tail.  Also, a
similar operation on two L<strings|/string>.

=item conditional

Something "iffy".  See L</Boolean context>.

=item connection

In telephony, the temporary electrical circuit between the caller's
and the callee's phone.  In networking, the same kind of temporary
circuit between a L</client> and a L</server>.

=item construct

As a noun, a piece of syntax made up of smaller pieces.  As a
transitive verb, to create an L</object> using a L</constructor>.

=item constructor

Any L</class method>, instance L</method>, or L</subroutine>
that composes, initializes, blesses, and returns an L</object>.
Sometimes we use the term loosely to mean a L</composer>.

=item context

The surroundings, or environment.  The context given by the
surrounding code determines what kind of data a particular
L</expression> is expected to return.  The three primary contexts are
L</list context>, L</scalar context>, and L</void context>.  Scalar
context is sometimes subdivided into L</Boolean context>, L</numeric
context>, L</string context>, and L</void context>.  There's also a
"don't care" scalar context (which is dealt with in Programming Perl,
Third Edition, Chapter 2, "Bits and Pieces" if you care).

=item continuation

The treatment of more than one physical L</line> as a single logical
line.  L</Makefile> lines are continued by putting a backslash before
the L</newline>.  Mail headers as defined by RFC 822 are continued by
putting a space or tab I<after> the newline.  In general, lines in
Perl do not need any form of continuation mark, because L</whitespace>
(including newlines) is gleefully ignored.  Usually.

=item core dump

The corpse of a L</process>, in the form of a file left in the
L</working directory> of the process, usually as a result of certain
kinds of fatal error.

=item CPAN

The Comprehensive Perl Archive Network.  (See L<perlfaq2/What modules and extensions are available for Perl?  What is CPAN?  What does CPANE<sol>srcE<sol>... mean?>).

=item cracker

Someone who breaks security on computer systems.  A cracker may be a
true L</hacker> or only a L</script kiddie>.

=item current package

The L</package> in which the current statement is compiled.  Scan
backwards in the text of your program through the current L<lexical
scope|/lexical scoping> or any enclosing lexical scopes till you find
a package declaration.  That's your current package name.

=item current working directory

See L</working directory>.

=item currently selected output channel

The last L</filehandle> that was designated with
L<select|perlfunc/select>(C<FILEHANDLE>); L</STDOUT>, if no filehandle
has been selected.

=item CV

An internal "code value" typedef, holding a L</subroutine>.  The L</CV>
type is a subclass of L</SV>.

=back

=head2 D

=over 4

=item dangling statement

A bare, single L</statement>, without any braces, hanging off an C<if>
or C<while> conditional.  C allows them.  Perl doesn't.

=item data structure

How your various pieces of data relate to each other and what shape
they make when you put them all together, as in a rectangular table or
a triangular-shaped tree.

=item data type

A set of possible values, together with all the operations that know
how to deal with those values.  For example, a numeric data type has a
certain set of numbers that you can work with and various mathematical
operations that you can do on the numbers but would make little sense
on, say, a string such as C<"Kilroy">.  Strings have their own
operations, such as L</concatenation>.  Compound types made of a
number of smaller pieces generally have operations to compose and
decompose them, and perhaps to rearrange them.  L<Objects|/object>
that model things in the real world often have operations that
correspond to real activities.  For instance, if you model an
elevator, your elevator object might have an C<open_door()>
L</method>.

=item datagram

A packet of data, such as a L</UDP> message, that (from the viewpoint
of the programs involved) can be sent independently over the network.
(In fact, all packets are sent independently at the L</IP> level, but
L</stream> protocols such as L</TCP> hide this from your program.)

=item DBM

Stands for "Data Base Management" routines, a set of routines that
emulate an L</associative array> using disk files.  The routines use a
dynamic hashing scheme to locate any entry with only two disk
accesses.  DBM files allow a Perl program to keep a persistent
L</hash> across multiple invocations.  You can L<tie|perlfunc/tie>
your hash variables to various DBM implementations--see L<AnyDBM_File>
and L<DB_File>.

=item declaration

An L</assertion> that states something exists and perhaps describes
what it's like, without giving any commitment as to how or where
you'll use it.  A declaration is like the part of your recipe that
says, "two cups flour, one large egg, four or five tadpoles..."  See
L</statement> for its opposite.  Note that some declarations also
function as statements.  Subroutine declarations also act as
definitions if a body is supplied.

=item decrement

To subtract a value from a variable, as in "decrement C<$x>" (meaning
to remove 1 from its value) or "decrement C<$x> by 3".

=item default

A L</value> chosen for you if you don't supply a value of your own.

=item defined

Having a meaning.  Perl thinks that some of the things people try to
do are devoid of meaning, in particular, making use of variables that
have never been given a L</value> and performing certain operations on
data that isn't there.  For example, if you try to read data past the
end of a file, Perl will hand you back an undefined value.  See also
L</false> and L<perlfunc/defined>.

=item delimiter

A L</character> or L</string> that sets bounds to an arbitrarily-sized
textual object, not to be confused with a L</separator> or
L</terminator>.  "To delimit" really just means "to surround" or "to
enclose" (like these parentheses are doing).

=item deprecated modules and features

Deprecated modules and features are those which were part of a stable
release, but later found to be subtly flawed, and which should be avoided.
They are subject to removal and/or bug-incompatible reimplementation in
the next major release (but they will be preserved through maintenance
releases).  Deprecation warnings are issued under B<-w> or C<use
diagnostics>, and notices are found in L<perldelta>s, as well as various
other PODs. Coding practices that misuse features, such as C<my $foo if
0>, can also be deprecated.

=item dereference

A fancy computer science term meaning "to follow a L</reference> to
what it points to".  The "de" part of it refers to the fact that
you're taking away one level of L</indirection>.

=item derived class

A L</class> that defines some of its L<methods|/method> in terms of a
more generic class, called a L</base class>.  Note that classes aren't
classified exclusively into base classes or derived classes: a class
can function as both a derived class and a base class simultaneously,
which is kind of classy.

=item descriptor

See L</file descriptor>.

=item destroy

To deallocate the memory of a L</referent> (first triggering its
C<DESTROY> method, if it has one).

=item destructor

A special L</method> that is called when an L</object> is thinking
about L<destroying|/destroy> itself.  A Perl program's C<DESTROY>
method doesn't do the actual destruction; Perl just
L<triggers|/trigger> the method in case the L</class> wants to do any
associated cleanup.

=item device

A whiz-bang hardware gizmo (like a disk or tape drive or a modem or a
joystick or a mouse) attached to your computer, that the L</operating
system> tries to make look like a L</file> (or a bunch of files).
Under Unix, these fake files tend to live in the I</dev> directory.

=item directive

A L</pod> directive.  See L<perlpod>.

=item directory

A special file that contains other files.  Some L<operating
systems|/operating system> call these "folders", "drawers", or
"catalogs".

=item directory handle

A name that represents a particular instance of opening a directory to
read it, until you close it.  See the L<opendir|perlfunc/opendir>
function.

=item dispatch

To send something to its correct destination.  Often used
metaphorically to indicate a transfer of programmatic control to a
destination selected algorithmically, often by lookup in a table of
function L<references|/reference> or, in the case of object
L<methods|/method>, by traversing the inheritance tree looking for the
most specific definition for the method.

=item distribution

A standard, bundled release of a system of software.  The default
usage implies source code is included.  If that is not the case, it
will be called a "binary-only" distribution.

=item (to be) dropped modules

When Perl 5 was first released (see L<perlhist>), several modules were
included, which have now fallen out of common use.  It has been suggested
that these modules should be removed, since the distribution became rather
large, and the common criterion for new module additions is now limited to
modules that help to build, test, and extend perl itself.  Furthermore,
the CPAN (which didn't exist at the time of Perl 5.0) can become the new
home of dropped modules. Dropping modules is currently not an option, but
further developments may clear the last barriers.

=item dweomer

An enchantment, illusion, phantasm, or jugglery.  Said when Perl's
magical L</dwimmer> effects don't do what you expect, but rather seem
to be the product of arcane dweomercraft, sorcery, or wonder working.
[From Old English]

=item dwimmer

DWIM is an acronym for "Do What I Mean", the principle that something
should just do what you want it to do without an undue amount of fuss.
A bit of code that does "dwimming" is a "dwimmer".  Dwimming can
require a great deal of behind-the-scenes magic, which (if it doesn't
stay properly behind the scenes) is called a L</dweomer> instead.

=item dynamic scoping

Dynamic scoping works over a dynamic scope, making variables visible
throughout the rest of the L</block> in which they are first used and
in any L<subroutines|/subroutine> that are called by the rest of the
block.  Dynamically scoped variables can have their values temporarily
changed (and implicitly restored later) by a L<local|perlfunc/local>
operator.  (Compare L</lexical scoping>.)  Used more loosely to mean
how a subroutine that is in the middle of calling another subroutine
"contains" that subroutine at L</run time>.

=back

=head2 E

=over 4

=item eclectic

Derived from many sources.  Some would say I<too> many.

=item element

A basic building block.  When you're talking about an L</array>, it's
one of the items that make up the array.

=item embedding

When something is contained in something else, particularly when that
might be considered surprising: "I've embedded a complete Perl
interpreter in my editor!"

=item empty subclass test

The notion that an empty L</derived class> should behave exactly like
its L</base class>.

=item en passant

When you change a L</value> as it is being copied.  [From French, "in
passing", as in the exotic pawn-capturing maneuver in chess.]

=item encapsulation

The veil of abstraction separating the L</interface> from the
L</implementation> (whether enforced or not), which mandates that all
access to an L</object>'s state be through L<methods|/method> alone.

=item endian

See L</little-endian> and L</big-endian>.

=item environment

The collective set of L<environment variables|/environment variable>
your L</process> inherits from its parent.  Accessed via C<%ENV>.

=item environment variable

A mechanism by which some high-level agent such as a user can pass its
preferences down to its future offspring (child L<processes|/process>,
grandchild processes, great-grandchild processes, and so on).  Each
environment variable is a L</key>/L</value> pair, like one entry in a
L</hash>.

=item EOF

End of File.  Sometimes used metaphorically as the terminating string
of a L</here document>.

=item errno

The error number returned by a L</syscall> when it fails.  Perl refers
to the error by the name C<$!> (or C<$OS_ERROR> if you use the English
module).

=item error

See L</exception> or L</fatal error>.

=item escape sequence

See L</metasymbol>.

=item exception

A fancy term for an error.  See L</fatal error>.

=item exception handling

The way a program responds to an error.  The exception handling
mechanism in Perl is the L<eval|perlfunc/eval> operator.

=item exec

To throw away the current L</process>'s program and replace it with
another without exiting the process or relinquishing any resources
held (apart from the old memory image).

=item executable file

A L</file> that is specially marked to tell the L</operating system>
that it's okay to run this file as a program.  Usually shortened to
"executable".

=item execute

To run a L<program|/executable file> or L</subroutine>.  (Has nothing
to do with the L<kill|perlfunc/kill> built-in, unless you're trying to
run a L</signal handler>.)

=item execute bit

The special mark that tells the operating system it can run this
program.  There are actually three execute bits under Unix, and which
bit gets used depends on whether you own the file singularly,
collectively, or not at all.

=item exit status

See L</status>.

=item export

To make symbols from a L</module> available for L</import> by other modules.

=item expression

Anything you can legally say in a spot where a L</value> is required.
Typically composed of L<literals|/literal>, L<variables|/variable>,
L<operators|/operator>, L<functions|/function>, and L</subroutine>
calls, not necessarily in that order.

=item extension

A Perl module that also pulls in compiled C or C++ code.  More
generally, any experimental option that can be compiled into Perl,
such as multithreading.

=back

=head2 F

=over 4

=item false

In Perl, any value that would look like C<""> or C<"0"> if evaluated
in a string context.  Since undefined values evaluate to C<"">, all
undefined values are false, but not all false values are undefined.

=item FAQ

Frequently Asked Question (although not necessarily frequently
answered, especially if the answer appears in the Perl FAQ shipped
standard with Perl).

=item fatal error

An uncaught L</exception>, which causes termination of the L</process>
after printing a message on your L</standard error> stream.  Errors
that happen inside an L<eval|perlfunc/eval> are not fatal.  Instead,
the L<eval|perlfunc/eval> terminates after placing the exception
message in the C<$@> (C<$EVAL_ERROR>) variable.  You can try to
provoke a fatal error with the L<die|perlfunc/die> operator (known as
throwing or raising an exception), but this may be caught by a
dynamically enclosing L<eval|perlfunc/eval>.  If not caught, the
L<die|perlfunc/die> becomes a fatal error.

=item field

A single piece of numeric or string data that is part of a longer
L</string>, L</record>, or L</line>.  Variable-width fields are usually
split up by L<separators|/separator> (so use L<split|perlfunc/split> to
extract the fields), while fixed-width fields are usually at fixed
positions (so use L<unpack|perlfunc/unpack>).  L<Instance
variables|/instance variable> are also known as fields.

=item FIFO

First In, First Out.  See also L</LIFO>.  Also, a nickname for a
L</named pipe>.

=item file

A named collection of data, usually stored on disk in a L</directory>
in a L</filesystem>.  Roughly like a document, if you're into office
metaphors.  In modern filesystems, you can actually give a file more
than one name.  Some files have special properties, like directories
and devices.

=item file descriptor

The little number the L</operating system> uses to keep track of which
opened L</file> you're talking about.  Perl hides the file descriptor
inside a L</standard IE<sol>O> stream and then attaches the stream to
a L</filehandle>.

=item file test operator

A built-in unary operator that you use to determine whether something
is L</true> about a file, such as C<-o $filename> to test whether
you're the owner of the file.

=item fileglob

A "wildcard" match on L<filenames|/filename>.  See the
L<glob|perlfunc/glob> function.

=item filehandle

An identifier (not necessarily related to the real name of a file)
that represents a particular instance of opening a file until you
close it.  If you're going to open and close several different files
in succession, it's fine to open each of them with the same
filehandle, so you don't have to write out separate code to process
each file.

=item filename

One name for a file.  This name is listed in a L</directory>, and you
can use it in an L<open|perlfunc/open> to tell the L</operating
system> exactly which file you want to open, and associate the file
with a L</filehandle> which will carry the subsequent identity of that
file in your program, until you close it.

=item filesystem

A set of L<directories|/directory> and L<files|/file> residing on a
partition of the disk.  Sometimes known as a "partition".  You can
change the file's name or even move a file around from directory to
directory within a filesystem without actually moving the file itself,
at least under Unix.

=item filter

A program designed to take a L</stream> of input and transform it into
a stream of output.

=item flag

We tend to avoid this term because it means so many things.  It may
mean a command-line L</switch> that takes no argument
itself (such as Perl's B<-n> and B<-p>
flags) or, less frequently, a single-bit indicator (such as the
C<O_CREAT> and C<O_EXCL> flags used in
L<sysopen|perlfunc/sysopen>).

=item floating point

A method of storing numbers in "scientific notation", such that the
precision of the number is independent of its magnitude (the decimal
point "floats").  Perl does its numeric work with floating-point
numbers (sometimes called "floats"), when it can't get away with
using L<integers|/integer>.  Floating-point numbers are mere
approximations of real numbers.

=item flush

The act of emptying a L</buffer>, often before it's full.

=item FMTEYEWTK

Far More Than Everything You Ever Wanted To Know.  An exhaustive
treatise on one narrow topic, something of a super-L</FAQ>.  See Tom
for far more.

=item fork

To create a child L</process> identical to the parent process at its
moment of conception, at least until it gets ideas of its own.  A
thread with protected memory.

=item formal arguments

The generic names by which a L</subroutine> knows its
L<arguments|/argument>.  In many languages, formal arguments are
always given individual names, but in Perl, the formal arguments are
just the elements of an array.  The formal arguments to a Perl program
are C<$ARGV[0]>, C<$ARGV[1]>, and so on.  Similarly, the formal
arguments to a Perl subroutine are C<$_[0]>, C<$_[1]>, and so on.  You
may give the arguments individual names by assigning the values to a
L<my|perlfunc/my> list.  See also L</actual arguments>.

=item format

A specification of how many spaces and digits and things to put
somewhere so that whatever you're printing comes out nice and pretty.

=item freely available

Means you don't have to pay money to get it, but the copyright on it
may still belong to someone else (like Larry).

=item freely redistributable

Means you're not in legal trouble if you give a bootleg copy of it to
your friends and we find out about it.  In fact, we'd rather you gave
a copy to all your friends.

=item freeware

Historically, any software that you give away, particularly if you
make the source code available as well.  Now often called C<open
source software>.  Recently there has been a trend to use the term in
contradistinction to L</open source software>, to refer only to free
software released under the Free Software Foundation's GPL (General
Public License), but this is difficult to justify etymologically.

=item function

Mathematically, a mapping of each of a set of input values to a
particular output value.  In computers, refers to a L</subroutine> or
L</operator> that returns a L</value>.  It may or may not have input
values (called L<arguments|/argument>).

=item funny character

Someone like Larry, or one of his peculiar friends.  Also refers to
the strange prefixes that Perl requires as noun markers on its
variables.

=back

=head2 G

=over 4

=item garbage collection

A misnamed feature--it should be called, "expecting your mother to
pick up after you".  Strictly speaking, Perl doesn't do this, but it
relies on a reference-counting mechanism to keep things tidy.
However, we rarely speak strictly and will often refer to the
reference-counting scheme as a form of garbage collection.  (If it's
any comfort, when your interpreter exits, a "real" garbage collector
runs to make sure everything is cleaned up if you've been messy with
circular references and such.)

=item GID

Group ID--in Unix, the numeric group ID that the L</operating system>
uses to identify you and members of your L</group>.

=item glob

Strictly, the shell's C<*> character, which will match a "glob" of
characters when you're trying to generate a list of filenames.
Loosely, the act of using globs and similar symbols to do pattern
matching.  See also L</fileglob> and L</typeglob>.

=item global

Something you can see from anywhere, usually used of
L<variables|/variable> and L<subroutines|/subroutine> that are visible
everywhere in your program.  In Perl, only certain special variables
are truly global--most variables (and all subroutines) exist only in
the current L</package>.  Global variables can be declared with
L<our|perlfunc/our>.  See L<perlfunc/our>.

=item global destruction

The L</garbage collection> of globals (and the running of any
associated object destructors) that takes place when a Perl
L</interpreter> is being shut down.  Global destruction should not be
confused with the Apocalypse, except perhaps when it should.

=item glue language

A language such as Perl that is good at hooking things together that
weren't intended to be hooked together.

=item granularity

The size of the pieces you're dealing with, mentally speaking.

=item greedy

A L</subpattern> whose L</quantifier> wants to match as many things as
possible.

=item grep

Originally from the old Unix editor command for "Globally search for a
Regular Expression and Print it", now used in the general sense of any
kind of search, especially text searches.  Perl has a built-in
L<grep|perlfunc/grep> function that searches a list for elements
matching any given criterion, whereas the I<grep>(1) program searches
for lines matching a L</regular expression> in one or more files.

=item group

A set of users of which you are a member.  In some operating systems
(like Unix), you can give certain file access permissions to other
members of your group.

=item GV

An internal "glob value" typedef, holding a L</typeglob>.  The L</GV>
type is a subclass of L</SV>.

=back

=head2 H

=over 4

=item hacker

Someone who is brilliantly persistent in solving technical problems,
whether these involve golfing, fighting orcs, or programming.  Hacker
is a neutral term, morally speaking.  Good hackers are not to be
confused with evil L<crackers|/cracker> or clueless L<script
kiddies|/script kiddie>.  If you confuse them, we will presume that
you are either evil or clueless.

=item handler

A L</subroutine> or L</method> that is called by Perl when your
program needs to respond to some internal event, such as a L</signal>,
or an encounter with an operator subject to L</operator overloading>.
See also L</callback>.

=item hard reference

A L</scalar> L</value> containing the actual address of a
L</referent>, such that the referent's L</reference> count accounts
for it.  (Some hard references are held internally, such as the
implicit reference from one of a L</typeglob>'s variable slots to its
corresponding referent.)  A hard reference is different from a
L</symbolic reference>.

=item hash

An unordered association of L</key>/L</value> pairs, stored such that
you can easily use a string L</key> to look up its associated data
L</value>.  This glossary is like a hash, where the word to be defined
is the key, and the definition is the value.  A hash is also sometimes
septisyllabically called an "associative array", which is a pretty
good reason for simply calling it a "hash" instead.

=item hash table

A data structure used internally by Perl for implementing associative
arrays (hashes) efficiently.  See also L</bucket>.

=item header file

A file containing certain required definitions that you must include
"ahead" of the rest of your program to do certain obscure operations.
A C header file has a I<.h> extension.  Perl doesn't really have
header files, though historically Perl has sometimes used translated
I<.h> files with a I<.ph> extension.  See L<perlfunc/require>.
(Header files have been superseded by the L</module> mechanism.)

=item here document

So called because of a similar construct in L<shells|/shell> that
pretends that the L<lines|/line> following the L</command> are a
separate L</file> to be fed to the command, up to some terminating
string.  In Perl, however, it's just a fancy form of quoting.

=item hexadecimal

A number in base 16, "hex" for short.  The digits for 10 through 16
are customarily represented by the letters C<a> through C<f>.
Hexadecimal constants in Perl start with C<0x>.  See also
L<perlfunc/hex>.

=item home directory

The directory you are put into when you log in.  On a Unix system, the
name is often placed into C<$ENV{HOME}> or C<$ENV{LOGDIR}> by
I<login>, but you can also find it with C<(getpwuid($E<lt>))[7]>.
(Some platforms do not have a concept of a home directory.)

=item host

The computer on which a program or other data resides.

=item hubris

Excessive pride, the sort of thing Zeus zaps you for.  Also the
quality that makes you write (and maintain) programs that other people
won't want to say bad things about.  Hence, the third great virtue of
a programmer.  See also L</laziness> and L</impatience>.

=item HV

Short for a "hash value" typedef, which holds Perl's internal
representation of a hash.  The L</HV> type is a subclass of L</SV>.

=back

=head2 I

=over 4

=item identifier

A legally formed name for most anything in which a computer program
might be interested.  Many languages (including Perl) allow
identifiers that start with a letter and contain letters and digits.
Perl also counts the underscore character as a valid letter.  (Perl
also has more complicated names, such as L</qualified> names.)

=item impatience

The anger you feel when the computer is being lazy.  This makes you
write programs that don't just react to your needs, but actually
anticipate them.  Or at least that pretend to.  Hence, the second
great virtue of a programmer.  See also L</laziness> and L</hubris>.

=item implementation

How a piece of code actually goes about doing its job.  Users of the
code should not count on implementation details staying the same
unless they are part of the published L</interface>.

=item import

To gain access to symbols that are exported from another module.  See
L<perlfunc/use>.

=item increment

To increase the value of something by 1 (or by some other number, if
so specified).

=item indexing

In olden days, the act of looking up a L</key> in an actual index
(such as a phone book), but now merely the act of using any kind of
key or position to find the corresponding L</value>, even if no index
is involved.  Things have degenerated to the point that Perl's
L<index|perlfunc/index> function merely locates the position (index)
of one string in another.

=item indirect filehandle

An L</expression> that evaluates to something that can be used as a
L</filehandle>: a L</string> (filehandle name), a L</typeglob>, a
typeglob L</reference>, or a low-level L</IO> object.

=item indirect object

In English grammar, a short noun phrase between a verb and its direct
object indicating the beneficiary or recipient of the action.  In
Perl, C<print STDOUT "$foo\n";> can be understood as "verb
indirect-object object" where L</STDOUT> is the recipient of the
L<print|perlfunc/print> action, and C<"$foo"> is the object being
printed.  Similarly, when invoking a L</method>, you might place the
invocant between the method and its arguments:

  $gollum = new Pathetic::Creature "Smeagol";
  give $gollum "Fisssssh!";
  give $gollum "Precious!";

In modern Perl, calling methods this way is often considered bad practice and
to be avoided.

=item indirect object slot

The syntactic position falling between a method call and its arguments
when using the indirect object invocation syntax.  (The slot is
distinguished by the absence of a comma between it and the next
argument.) L</STDERR> is in the indirect object slot here:

  print STDERR "Awake!  Awake!  Fear, Fire,
      Foes!  Awake!\n";

=item indirection

If something in a program isn't the value you're looking for but
indicates where the value is, that's indirection.  This can be done
with either L<symbolic references|/symbolic reference> or L<hard
references|/hard reference>.

=item infix

An L</operator> that comes in between its L<operands|/operand>, such
as multiplication in C<24 * 7>.

=item inheritance

What you get from your ancestors, genetically or otherwise.  If you
happen to be a L</class>, your ancestors are called L<base
classes|/base class> and your descendants are called L<derived
classes|/derived class>.  See L</single inheritance> and L</multiple
inheritance>.

=item instance

Short for "an instance of a class", meaning an L</object> of that L</class>.

=item instance variable

An L</attribute> of an L</object>; data stored with the particular
object rather than with the class as a whole.

=item integer

A number with no fractional (decimal) part.  A counting number, like
1, 2, 3, and so on, but including 0 and the negatives.

=item interface

The services a piece of code promises to provide forever, in contrast to
its L</implementation>, which it should feel free to change whenever it
likes.

=item interpolation

The insertion of a scalar or list value somewhere in the middle of
another value, such that it appears to have been there all along.  In
Perl, variable interpolation happens in double-quoted strings and
patterns, and list interpolation occurs when constructing the list of
values to pass to a list operator or other such construct that takes a
L</LIST>.

=item interpreter

Strictly speaking, a program that reads a second program and does what
the second program says directly without turning the program into a
different form first, which is what L<compilers|/compiler> do.  Perl
is not an interpreter by this definition, because it contains a kind
of compiler that takes a program and turns it into a more executable
form (L<syntax trees|/syntax tree>) within the I<perl> process itself,
which the Perl L</run time> system then interprets.

=item invocant

The agent on whose behalf a L</method> is invoked.  In a L</class>
method, the invocant is a package name.  In an L</instance> method,
the invocant is an object reference.

=item invocation

The act of calling up a deity, daemon, program, method, subroutine, or
function to get it do what you think it's supposed to do.  We usually
"call" subroutines but "invoke" methods, since it sounds cooler.

=item I/O

Input from, or output to, a L</file> or L</device>.

=item IO

An internal I/O object.  Can also mean L</indirect object>.

=item IP

Internet Protocol, or Intellectual Property.

=item IPC

Interprocess Communication.

=item is-a

A relationship between two L<objects|/object> in which one object is
considered to be a more specific version of the other, generic object:
"A camel is a mammal."  Since the generic object really only exists in
a Platonic sense, we usually add a little abstraction to the notion of
objects and think of the relationship as being between a generic
L</base class> and a specific L</derived class>.  Oddly enough,
Platonic classes don't always have Platonic relationships--see
L</inheritance>.

=item iteration

Doing something repeatedly.

=item iterator

A special programming gizmo that keeps track of where you are in
something that you're trying to iterate over.  The C<foreach> loop in
Perl contains an iterator; so does a hash, allowing you to
L<each|perlfunc/each> through it.

=item IV

The integer four, not to be confused with six, Tom's favorite editor.
IV also means an internal Integer Value of the type a L</scalar> can
hold, not to be confused with an L</NV>.

=back

=head2 J

=over 4

=item JAPH

"Just Another Perl Hacker," a clever but cryptic bit of Perl code that
when executed, evaluates to that string.  Often used to illustrate a
particular Perl feature, and something of an ongoing Obfuscated Perl
Contest seen in Usenix signatures.

=back

=head2 K

=over 4

=item key

The string index to a L</hash>, used to look up the L</value>
associated with that key.

=item keyword

See L</reserved words>.

=back

=head2 L

=over 4

=item label

A name you give to a L</statement> so that you can talk about that
statement elsewhere in the program.

=item laziness

The quality that makes you go to great effort to reduce overall energy
expenditure.  It makes you write labor-saving programs that other
people will find useful, and document what you wrote so you don't have
to answer so many questions about it.  Hence, the first great virtue
of a programmer.  Also hence, this book.  See also L</impatience> and
L</hubris>.

=item left shift

A L</bit shift> that multiplies the number by some power of 2.

=item leftmost longest

The preference of the L</regular expression> engine to match the
leftmost occurrence of a L</pattern>, then given a position at which a
match will occur, the preference for the longest match (presuming the
use of a L</greedy> quantifier).  See L<perlre> for I<much> more on
this subject.

=item lexeme

Fancy term for a L</token>.

=item lexer

Fancy term for a L</tokener>.

=item lexical analysis

Fancy term for L</tokenizing>.

=item lexical scoping

Looking at your I<Oxford English Dictionary> through a microscope.
(Also known as L</static scoping>, because dictionaries don't change
very fast.)  Similarly, looking at variables stored in a private
dictionary (namespace) for each scope, which are visible only from
their point of declaration down to the end of the lexical scope in
which they are declared.  --Syn. L</static scoping>.
--Ant. L</dynamic scoping>.

=item lexical variable

A L</variable> subject to L</lexical scoping>, declared by
L<my|perlfunc/my>.  Often just called a "lexical".  (The
L<our|perlfunc/our> declaration declares a lexically scoped name for a
global variable, which is not itself a lexical variable.)

=item library

Generally, a collection of procedures.  In ancient days, referred to a
collection of subroutines in a I<.pl> file.  In modern times, refers
more often to the entire collection of Perl L<modules|/module> on your
system.

=item LIFO

Last In, First Out.  See also L</FIFO>.  A LIFO is usually called a
L</stack>.

=item line

In Unix, a sequence of zero or more non-newline characters terminated
with a L</newline> character.  On non-Unix machines, this is emulated
by the C library even if the underlying L</operating system> has
different ideas.

=item line buffering

Used by a L</standard IE<sol>O> output stream that flushes its
L</buffer> after every L</newline>.  Many standard I/O libraries
automatically set up line buffering on output that is going to the
terminal.

=item line number

The number of lines read previous to this one, plus 1.  Perl keeps a
separate line number for each source or input file it opens.  The
current source file's line number is represented by C<__LINE__>.  The
current input line number (for the file that was most recently read
via C<< E<lt>FHE<gt> >>) is represented by the C<$.>
(C<$INPUT_LINE_NUMBER>) variable.  Many error messages report both
values, if available.

=item link

Used as a noun, a name in a L</directory>, representing a L</file>.  A
given file can have multiple links to it.  It's like having the same
phone number listed in the phone directory under different names.  As
a verb, to resolve a partially compiled file's unresolved symbols into
a (nearly) executable image.  Linking can generally be static or
dynamic, which has nothing to do with static or dynamic scoping.

=item LIST

A syntactic construct representing a comma-separated list of
expressions, evaluated to produce a L</list value>.  Each
L</expression> in a L</LIST> is evaluated in L</list context> and
interpolated into the list value.

=item list

An ordered set of scalar values.

=item list context

The situation in which an L</expression> is expected by its
surroundings (the code calling it) to return a list of values rather
than a single value.  Functions that want a L</LIST> of arguments tell
those arguments that they should produce a list value.  See also
L</context>.

=item list operator

An L</operator> that does something with a list of values, such as
L<join|perlfunc/join> or L<grep|perlfunc/grep>.  Usually used for
named built-in operators (such as L<print|perlfunc/print>,
L<unlink|perlfunc/unlink>, and L<system|perlfunc/system>) that do not
require parentheses around their L</argument> list.

=item list value

An unnamed list of temporary scalar values that may be passed around
within a program from any list-generating function to any function or
construct that provides a L</list context>.

=item literal

A token in a programming language such as a number or L</string> that
gives you an actual L</value> instead of merely representing possible
values as a L</variable> does.

=item little-endian

From Swift: someone who eats eggs little end first.  Also used of
computers that store the least significant L</byte> of a word at a
lower byte address than the most significant byte.  Often considered
superior to big-endian machines.  See also L</big-endian>.

=item local

Not meaning the same thing everywhere.  A global variable in Perl can
be localized inside a L<dynamic scope|/dynamic scoping> via the
L<local|perlfunc/local> operator.

=item logical operator

Symbols representing the concepts "and", "or", "xor", and "not".

=item lookahead

An L</assertion> that peeks at the string to the right of the current
match location.

=item lookbehind

An L</assertion> that peeks at the string to the left of the current
match location.

=item loop

A construct that performs something repeatedly, like a roller coaster.

=item loop control statement

Any statement within the body of a loop that can make a loop
prematurely stop looping or skip an L</iteration>.  Generally you
shouldn't try this on roller coasters.

=item loop label

A kind of key or name attached to a loop (or roller coaster) so that
loop control statements can talk about which loop they want to
control.

=item lvaluable

Able to serve as an L</lvalue>.

=item lvalue

Term used by language lawyers for a storage location you can assign a
new L</value> to, such as a L</variable> or an element of an
L</array>.  The "l" is short for "left", as in the left side of an
assignment, a typical place for lvalues.  An L</lvaluable> function or
expression is one to which a value may be assigned, as in C<pos($x) =
10>.

=item lvalue modifier

An adjectival pseudofunction that warps the meaning of an L</lvalue>
in some declarative fashion.  Currently there are three lvalue
modifiers: L<my|perlfunc/my>, L<our|perlfunc/our>, and
L<local|perlfunc/local>.

=back

=head2 M

=over 4

=item magic

Technically speaking, any extra semantics attached to a variable such
as C<$!>, C<$0>, C<%ENV>, or C<%SIG>, or to any tied variable.
Magical things happen when you diddle those variables.

=item magical increment

An L</increment> operator that knows how to bump up alphabetics as
well as numbers.

=item magical variables

Special variables that have side effects when you access them or
assign to them.  For example, in Perl, changing elements of the
C<%ENV> array also changes the corresponding environment variables
that subprocesses will use.  Reading the C<$!> variable gives you the
current system error number or message.

=item Makefile

A file that controls the compilation of a program.  Perl programs
don't usually need a L</Makefile> because the Perl compiler has plenty
of self-control.

=item man

The Unix program that displays online documentation (manual pages) for
you.

=item manpage

A "page" from the manuals, typically accessed via the I<man>(1)
command.  A manpage contains a SYNOPSIS, a DESCRIPTION, a list of
BUGS, and so on, and is typically longer than a page.  There are
manpages documenting L<commands|/command>, L<syscalls|/syscall>,
L</library> L<functions|/function>, L<devices|/device>,
L<protocols|/protocol>, L<files|/file>, and such.  In this book, we
call any piece of standard Perl documentation (like I<perlop> or
I<perldelta>) a manpage, no matter what format it's installed in on
your system.

=item matching

See L</pattern matching>.

=item member data

See L</instance variable>.

=item memory

This always means your main memory, not your disk.  Clouding the issue
is the fact that your machine may implement L</virtual> memory; that
is, it will pretend that it has more memory than it really does, and
it'll use disk space to hold inactive bits.  This can make it seem
like you have a little more memory than you really do, but it's not a
substitute for real memory.  The best thing that can be said about
virtual memory is that it lets your performance degrade gradually
rather than suddenly when you run out of real memory.  But your
program can die when you run out of virtual memory too, if you haven't
thrashed your disk to death first.

=item metacharacter

A L</character> that is I<not> supposed to be treated normally.  Which
characters are to be treated specially as metacharacters varies
greatly from context to context.  Your L</shell> will have certain
metacharacters, double-quoted Perl L<strings|/string> have other
metacharacters, and L</regular expression> patterns have all the
double-quote metacharacters plus some extra ones of their own.

=item metasymbol

Something we'd call a L</metacharacter> except that it's a sequence of
more than one character.  Generally, the first character in the
sequence must be a true metacharacter to get the other characters in
the metasymbol to misbehave along with it.

=item method

A kind of action that an L</object> can take if you tell it to.  See
L<perlobj>.

=item minimalism

The belief that "small is beautiful."  Paradoxically, if you say
something in a small language, it turns out big, and if you say it in
a big language, it turns out small.  Go figure.

=item mode

In the context of the L<stat> syscall, refers to the field holding
the L</permission bits> and the type of the L</file>.

=item modifier

See L</statement modifier>, L</regular expression modifier>, and
L</lvalue modifier>, not necessarily in that order.

=item module

A L</file> that defines a L</package> of (almost) the same name, which
can either L</export> symbols or function as an L</object> class.  (A
module's main I<.pm> file may also load in other files in support of
the module.)  See the L<use|perlfunc/use> built-in.

=item modulus

An integer divisor when you're interested in the remainder instead of
the quotient.

=item monger

Short for Perl Monger, a purveyor of Perl.

=item mortal

A temporary value scheduled to die when the current statement
finishes.

=item multidimensional array

An array with multiple subscripts for finding a single element.  Perl
implements these using L<references|/reference>--see L<perllol> and
L<perldsc>.

=item multiple inheritance

The features you got from your mother and father, mixed together
unpredictably.  (See also L</inheritance>, and L</single
inheritance>.)  In computer languages (including Perl), the notion
that a given class may have multiple direct ancestors or L<base
classes|/base class>.

=back

=head2 N

=over 4

=item named pipe

A L</pipe> with a name embedded in the L</filesystem> so that it can
be accessed by two unrelated L<processes|/process>.

=item namespace

A domain of names.  You needn't worry about whether the names in one
such domain have been used in another.  See L</package>.

=item network address

The most important attribute of a socket, like your telephone's
telephone number.  Typically an IP address.  See also L</port>.

=item newline

A single character that represents the end of a line, with the ASCII
value of 012 octal under Unix (but 015 on a Mac), and represented by
C<\n> in Perl strings.  For Windows machines writing text files, and
for certain physical devices like terminals, the single newline gets
automatically translated by your C library into a line feed and a
carriage return, but normally, no translation is done.

=item NFS

Network File System, which allows you to mount a remote filesystem as
if it were local.

=item null character

A character with the ASCII value of zero.  It's used by C to terminate
strings, but Perl allows strings to contain a null.

=item null list

A L</list value> with zero elements, represented in Perl by C<()>.

=item null string

A L</string> containing no characters, not to be confused with a
string containing a L</null character>, which has a positive length
and is L</true>.

=item numeric context

The situation in which an expression is expected by its surroundings
(the code calling it) to return a number.  See also L</context> and
L</string context>.

=item NV

Short for Nevada, no part of which will ever be confused with
civilization.  NV also means an internal floating-point Numeric Value
of the type a L</scalar> can hold, not to be confused with an L</IV>.

=item nybble

Half a L</byte>, equivalent to one L</hexadecimal> digit, and worth
four L<bits|/bit>.

=back

=head2 O

=over 4

=item object

An L</instance> of a L</class>.  Something that "knows" what
user-defined type (class) it is, and what it can do because of what
class it is.  Your program can request an object to do things, but the
object gets to decide whether it wants to do them or not.  Some
objects are more accommodating than others.

=item octal

A number in base 8.  Only the digits 0 through 7 are allowed.  Octal
constants in Perl start with 0, as in 013.  See also the
L<oct|perlfunc/oct> function.

=item offset

How many things you have to skip over when moving from the beginning
of a string or array to a specific position within it.  Thus, the
minimum offset is zero, not one, because you don't skip anything to
get to the first item.

=item one-liner

An entire computer program crammed into one line of text.

=item open source software

Programs for which the source code is freely available and freely
redistributable, with no commercial strings attached.  For a more
detailed definition, see L<http://www.opensource.org/osd.html>.

=item operand

An L</expression> that yields a L</value> that an L</operator>
operates on.  See also L</precedence>.

=item operating system

A special program that runs on the bare machine and hides the gory
details of managing L<processes|/process> and L<devices|/device>.
Usually used in a looser sense to indicate a particular culture of
programming.  The loose sense can be used at varying levels of
specificity.  At one extreme, you might say that all versions of Unix
and Unix-lookalikes are the same operating system (upsetting many
people, especially lawyers and other advocates).  At the other
extreme, you could say this particular version of this particular
vendor's operating system is different from any other version of this
or any other vendor's operating system.  Perl is much more portable
across operating systems than many other languages.  See also
L</architecture> and L</platform>.

=item operator

A gizmo that transforms some number of input values to some number of
output values, often built into a language with a special syntax or
symbol.  A given operator may have specific expectations about what
L<types|/type> of data you give as its arguments
(L<operands|/operand>) and what type of data you want back from it.

=item operator overloading

A kind of L</overloading> that you can do on built-in
L<operators|/operator> to make them work on L<objects|/object> as if
the objects were ordinary scalar values, but with the actual semantics
supplied by the object class.  This is set up with the L<overload>
L</pragma>.

=item options

See either L<switches|/switch> or L</regular expression modifier>.

=item ordinal

Another name for L</code point>

=item overloading

Giving additional meanings to a symbol or construct.  Actually, all
languages do overloading to one extent or another, since people are
good at figuring out things from L</context>.

=item overriding

Hiding or invalidating some other definition of the same name.  (Not
to be confused with L</overloading>, which adds definitions that must
be disambiguated some other way.) To confuse the issue further, we use
the word with two overloaded definitions: to describe how you can
define your own L</subroutine> to hide a built-in L</function> of the
same name (see L<perlsub/Overriding Built-in Functions>) and to
describe how you can define a replacement L</method> in a L</derived
class> to hide a L</base class>'s method of the same name (see
L<perlobj>).

=item owner

The one user (apart from the superuser) who has absolute control over
a L</file>.  A file may also have a L</group> of users who may
exercise joint ownership if the real owner permits it.  See
L</permission bits>.

=back

=head2 P

=over 4

=item package

A L</namespace> for global L<variables|/variable>,
L<subroutines|/subroutine>, and the like, such that they can be kept
separate from like-named L<symbols|/symbol> in other namespaces.  In a
sense, only the package is global, since the symbols in the package's
symbol table are only accessible from code compiled outside the
package by naming the package.  But in another sense, all package
symbols are also globals--they're just well-organized globals.

=item pad

Short for L</scratchpad>.

=item parameter

See L</argument>.

=item parent class

See L</base class>.

=item parse tree

See L</syntax tree>.

=item parsing

The subtle but sometimes brutal art of attempting to turn your
possibly malformed program into a valid L</syntax tree>.

=item patch

To fix by applying one, as it were.  In the realm of hackerdom, a
listing of the differences between two versions of a program as might
be applied by the I<patch>(1) program when you want to fix a bug or
upgrade your old version.

=item PATH

The list of L<directories|/directory> the system searches to find a
program you want to L</execute>.  The list is stored as one of your
L<environment variables|/environment variable>, accessible in Perl as
C<$ENV{PATH}>.

=item pathname

A fully qualified filename such as I</usr/bin/perl>.  Sometimes
confused with L</PATH>.

=item pattern

A template used in L</pattern matching>.

=item pattern matching

Taking a pattern, usually a L</regular expression>, and trying the
pattern various ways on a string to see whether there's any way to
make it fit.  Often used to pick interesting tidbits out of a file.

=item permission bits

Bits that the L</owner> of a file sets or unsets to allow or disallow
access to other people.  These flag bits are part of the L</mode> word
returned by the L<stat|perlfunc/stat> built-in when you ask about a
file.  On Unix systems, you can check the I<ls>(1) manpage for more
information.

=item Pern

What you get when you do C<Perl++> twice.  Doing it only once will
curl your hair.  You have to increment it eight times to shampoo your
hair.  Lather, rinse, iterate.

=item pipe

A direct L</connection> that carries the output of one L</process> to
the input of another without an intermediate temporary file.  Once the
pipe is set up, the two processes in question can read and write as if
they were talking to a normal file, with some caveats.

=item pipeline

A series of L<processes|/process> all in a row, linked by
L<pipes|/pipe>, where each passes its output stream to the next.

=item platform

The entire hardware and software context in which a program runs.  A
 program written in a platform-dependent language might break if you
change any of: machine, operating system, libraries, compiler, or
system configuration.  The I<perl> interpreter has to be compiled
differently for each platform because it is implemented in C, but
programs written in the Perl language are largely
platform-independent.

=item pod

The markup used to embed documentation into your Perl code.  See
L<perlpod>.

=item pointer

A L</variable> in a language like C that contains the exact memory
location of some other item.  Perl handles pointers internally so you
don't have to worry about them.  Instead, you just use symbolic
pointers in the form of L<keys|/key> and L</variable> names, or L<hard
references|/hard reference>, which aren't pointers (but act like
pointers and do in fact contain pointers).

=item polymorphism

The notion that you can tell an L</object> to do something generic,
and the object will interpret the command in different ways depending
on its type.  [E<lt>Gk many shapes]

=item port

The part of the address of a TCP or UDP socket that directs packets to
the correct process after finding the right machine, something like
the phone extension you give when you reach the company operator.
Also, the result of converting code to run on a different platform
than originally intended, or the verb denoting this conversion.

=item portable

Once upon a time, C code compilable under both BSD and SysV.  In
general, code that can be easily converted to run on another
L</platform>, where "easily" can be defined however you like, and
usually is.  Anything may be considered portable if you try hard
enough.  See I<mobile home> or I<London Bridge>.

=item porter

Someone who "carries" software from one L</platform> to another.
Porting programs written in platform-dependent languages such as C can
be difficult work, but porting programs like Perl is very much worth
the agony.

=item POSIX

The Portable Operating System Interface specification.

=item postfix

An L</operator> that follows its L</operand>, as in C<$x++>.

=item pp

An internal shorthand for a "push-pop" code, that is, C code
implementing Perl's stack machine.

=item pragma

A standard module whose practical hints and suggestions are received
(and possibly ignored) at compile time.  Pragmas are named in all
lowercase.

=item precedence

The rules of conduct that, in the absence of other guidance, determine
what should happen first.  For example, in the absence of parentheses,
you always do multiplication before addition.

=item prefix

An L</operator> that precedes its L</operand>, as in C<++$x>.

=item preprocessing

What some helper L</process> did to transform the incoming data into a
form more suitable for the current process.  Often done with an
incoming L</pipe>.  See also L</C preprocessor>.

=item procedure

A L</subroutine>.

=item process

An instance of a running program.  Under multitasking systems like
Unix, two or more separate processes could be running the same program
independently at the same time--in fact, the L<fork|perlfunc/fork>
function is designed to bring about this happy state of affairs.
Under other operating systems, processes are sometimes called
"threads", "tasks", or "jobs", often with slight nuances in meaning.

=item program generator

A system that algorithmically writes code for you in a high-level
language.  See also L</code generator>.

=item progressive matching

L<Pattern matching|/pattern matching> that picks up where it left off before.

=item property

See either L</instance variable> or L</character property>.

=item protocol

In networking, an agreed-upon way of sending messages back and forth
so that neither correspondent will get too confused.

=item prototype

An optional part of a L</subroutine> declaration telling the Perl
compiler how many and what flavor of arguments may be passed as
L</actual arguments>, so that you can write subroutine calls that
parse much like built-in functions.  (Or don't parse, as the case may
be.)

=item pseudofunction

A construct that sometimes looks like a function but really isn't.
Usually reserved for L</lvalue> modifiers like L<my|perlfunc/my>, for
L</context> modifiers like L<scalar|perlfunc/scalar>, and for the
pick-your-own-quotes constructs, C<q//>, C<qq//>, C<qx//>, C<qw//>,
C<qr//>, C<m//>, C<s///>, C<y///>, and C<tr///>.

=item pseudohash

A reference to an array whose initial element happens to hold a
reference to a hash.  You can treat a pseudohash reference as either
an array reference or a hash reference.

=item pseudoliteral

An L</operator> that looks something like a L</literal>, such as the
output-grabbing operator, C<`>I<C<command>>C<`>.

=item public domain

Something not owned by anybody.  Perl is copyrighted and is thus
I<not> in the public domain--it's just L</freely available> and
L</freely redistributable>.

=item pumpkin

A notional "baton" handed around the Perl community indicating who is
the lead integrator in some arena of development.

=item pumpking

A L</pumpkin> holder, the person in charge of pumping the pump, or at
least priming it.  Must be willing to play the part of the Great
Pumpkin now and then.

=item PV

A "pointer value", which is Perl Internals Talk for a C<char*>.

=back

=head2 Q

=over 4

=item qualified

Possessing a complete name.  The symbol C<$Ent::moot> is qualified;
C<$moot> is unqualified.  A fully qualified filename is specified from
the top-level directory.

=item quantifier

A component of a L</regular expression> specifying how many times the
foregoing L</atom> may occur.

=back

=head2 R

=over 4

=item readable

With respect to files, one that has the proper permission bit set to
let you access the file.  With respect to computer programs, one
that's written well enough that someone has a chance of figuring out
what it's trying to do.

=item reaping

The last rites performed by a parent L</process> on behalf of a
deceased child process so that it doesn't remain a L</zombie>.  See
the L<wait|perlfunc/wait> and L<waitpid|perlfunc/waitpid> function
calls.

=item record

A set of related data values in a L</file> or L</stream>, often
associated with a unique L</key> field.  In Unix, often commensurate
with a L</line>, or a blank-line-terminated set of lines (a
"paragraph").  Each line of the I</etc/passwd> file is a record, keyed
on login name, containing information about that user.

=item recursion

The art of defining something (at least partly) in terms of itself,
which is a naughty no-no in dictionaries but often works out okay in
computer programs if you're careful not to recurse forever, which is
like an infinite loop with more spectacular failure modes.

=item reference

Where you look to find a pointer to information somewhere else.  (See
L</indirection>.)  References come in two flavors, L<symbolic
references|/symbolic reference> and L<hard references|/hard
reference>.

=item referent

Whatever a reference refers to, which may or may not have a name.
Common types of referents include scalars, arrays, hashes, and
subroutines.

=item regex

See L</regular expression>.

=item regular expression

A single entity with various interpretations, like an elephant.  To a
computer scientist, it's a grammar for a little language in which some
strings are legal and others aren't.  To normal people, it's a pattern
you can use to find what you're looking for when it varies from case
to case.  Perl's regular expressions are far from regular in the
theoretical sense, but in regular use they work quite well.  Here's a
regular expression: C</Oh s.*t./>.  This will match strings like "C<Oh
say can you see by the dawn's early light>" and "C<Oh sit!>".  See
L<perlre>.

=item regular expression modifier

An option on a pattern or substitution, such as C</i> to render the
pattern case insensitive.  See also L</cloister>.

=item regular file

A L</file> that's not a L</directory>, a L</device>, a named L</pipe>
or L</socket>, or a L</symbolic link>.  Perl uses the C<-f> file test
operator to identify regular files.  Sometimes called a "plain" file.

=item relational operator

An L</operator> that says whether a particular ordering relationship
is L</true> about a pair of L<operands|/operand>.  Perl has both
numeric and string relational operators.  See L</collating sequence>.

=item reserved words

A word with a specific, built-in meaning to a L</compiler>, such as
C<if> or L<delete|perlfunc/delete>.  In many languages (not Perl),
it's illegal to use reserved words to name anything else.  (Which is
why they're reserved, after all.)  In Perl, you just can't use them to
name L<labels|/label> or L<filehandles|/filehandle>.  Also called
"keywords".

=item return value

The L</value> produced by a L</subroutine> or L</expression> when
evaluated.  In Perl, a return value may be either a L</list> or a
L</scalar>.

=item RFC

Request For Comment, which despite the timid connotations is the name
of a series of important standards documents.

=item right shift

A L</bit shift> that divides a number by some power of 2.

=item root

The superuser (UID == 0).  Also, the top-level directory of the
filesystem.

=item RTFM

What you are told when someone thinks you should Read The Fine Manual.

=item run phase

Any time after Perl starts running your main program.  See also
L</compile phase>.  Run phase is mostly spent in L</run time> but may
also be spent in L</compile time> when L<require|perlfunc/require>,
L<do|perlfunc/do> C<FILE>, or L<eval|perlfunc/eval> C<STRING>
operators are executed or when a substitution uses the C</ee>
modifier.

=item run time

The time when Perl is actually doing what your code says to do, as
opposed to the earlier period of time when it was trying to figure out
whether what you said made any sense whatsoever, which is L</compile
time>.

=item run-time pattern

A pattern that contains one or more variables to be interpolated
before parsing the pattern as a L</regular expression>, and that
therefore cannot be analyzed at compile time, but must be re-analyzed
each time the pattern match operator is evaluated.  Run-time patterns
are useful but expensive.

=item RV

A recreational vehicle, not to be confused with vehicular recreation.
RV also means an internal Reference Value of the type a L</scalar> can
hold.  See also L</IV> and L</NV> if you're not confused yet.

=item rvalue

A L</value> that you might find on the right side of an
L</assignment>.  See also L</lvalue>.

=back

=head2 S

=over 4

=item scalar

A simple, singular value; a number, L</string>, or L</reference>.

=item scalar context

The situation in which an L</expression> is expected by its
surroundings (the code calling it) to return a single L</value> rather
than a L</list> of values.  See also L</context> and L</list context>.
A scalar context sometimes imposes additional constraints on the
return value--see L</string context> and L</numeric context>.
Sometimes we talk about a L</Boolean context> inside conditionals, but
this imposes no additional constraints, since any scalar value,
whether numeric or L</string>, is already true or false.

=item scalar literal

A number or quoted L</string>--an actual L</value> in the text of your
program, as opposed to a L</variable>.

=item scalar value

A value that happens to be a L</scalar> as opposed to a L</list>.

=item scalar variable

A L</variable> prefixed with C<$> that holds a single value.

=item scope

How far away you can see a variable from, looking through one.  Perl
has two visibility mechanisms: it does L</dynamic scoping> of
L<local|perlfunc/local> L<variables|/variable>, meaning that the rest
of the L</block>, and any L<subroutines|/subroutine> that are called
by the rest of the block, can see the variables that are local to the
block.  Perl does L</lexical scoping> of L<my|perlfunc/my> variables,
meaning that the rest of the block can see the variable, but other
subroutines called by the block I<cannot> see the variable.

=item scratchpad

The area in which a particular invocation of a particular file or
subroutine keeps some of its temporary values, including any lexically
scoped variables.

=item script

A text L</file> that is a program intended to be L<executed|/execute>
directly rather than L<compiled|/compiler> to another form of file
before execution.  Also, in the context of L</Unicode>, a writing
system for a particular language or group of languages, such as Greek,
Bengali, or Klingon.

=item script kiddie

A L</cracker> who is not a L</hacker>, but knows just enough to run
canned scripts.  A cargo-cult programmer.

=item sed

A venerable Stream EDitor from which Perl derives some of its ideas.

=item semaphore

A fancy kind of interlock that prevents multiple L<threads|/thread> or
L<processes|/process> from using up the same resources simultaneously.

=item separator

A L</character> or L</string> that keeps two surrounding strings from
being confused with each other.  The L<split|perlfunc/split> function
works on separators.  Not to be confused with L<delimiters|/delimiter>
or L<terminators|/terminator>.  The "or" in the previous sentence
separated the two alternatives.

=item serialization

Putting a fancy L</data structure> into linear order so that it can be
stored as a L</string> in a disk file or database or sent through a
L</pipe>.  Also called marshalling.

=item server

In networking, a L</process> that either advertises a L</service> or
just hangs around at a known location and waits for L<clients|/client>
who need service to get in touch with it.

=item service

Something you do for someone else to make them happy, like giving them
the time of day (or of their life).  On some machines, well-known
services are listed by the L<getservent|perlfunc/getservent> function.

=item setgid

Same as L</setuid>, only having to do with giving away L</group>
privileges.

=item setuid

Said of a program that runs with the privileges of its L</owner>
rather than (as is usually the case) the privileges of whoever is
running it.  Also describes the bit in the mode word (L</permission
bits>) that controls the feature.  This bit must be explicitly set by
the owner to enable this feature, and the program must be carefully
written not to give away more privileges than it ought to.

=item shared memory

A piece of L</memory> accessible by two different
L<processes|/process> who otherwise would not see each other's memory.

=item shebang

Irish for the whole McGillicuddy.  In Perl culture, a portmanteau of
"sharp" and "bang", meaning the C<#!> sequence that tells the system
where to find the interpreter.

=item shell

A L</command>-line L</interpreter>.  The program that interactively
gives you a prompt, accepts one or more L<lines|/line> of input, and
executes the programs you mentioned, feeding each of them their proper
L<arguments|/argument> and input data.  Shells can also execute
scripts containing such commands.  Under Unix, typical shells include
the Bourne shell (I</bin/sh>), the C shell (I</bin/csh>), and the Korn
shell (I</bin/ksh>).  Perl is not strictly a shell because it's not
interactive (although Perl programs can be interactive).

=item side effects

Something extra that happens when you evaluate an L</expression>.
Nowadays it can refer to almost anything.  For example, evaluating a
simple assignment statement typically has the "side effect" of
assigning a value to a variable.  (And you thought assigning the value
was your primary intent in the first place!)  Likewise, assigning a
value to the special variable C<$|> (C<$AUTOFLUSH>) has the side
effect of forcing a flush after every L<write|perlfunc/write> or
L<print|perlfunc/print> on the currently selected filehandle.

=item signal

A bolt out of the blue; that is, an event triggered by the
L</operating system>, probably when you're least expecting it.

=item signal handler

A L</subroutine> that, instead of being content to be called in the
normal fashion, sits around waiting for a bolt out of the blue before
it will deign to L</execute>.  Under Perl, bolts out of the blue are
called signals, and you send them with the L<kill|perlfunc/kill>
built-in.  See L<perlvar/%SIG> and L<perlipc/Signals>.

=item single inheritance

The features you got from your mother, if she told you that you don't
have a father.  (See also L</inheritance> and L</multiple
inheritance>.)  In computer languages, the notion that
L<classes|/class> reproduce asexually so that a given class can only
have one direct ancestor or L</base class>.  Perl supplies no such
restriction, though you may certainly program Perl that way if you
like.

=item slice

A selection of any number of L<elements|/element> from a L</list>,
L</array>, or L</hash>.

=item slurp

To read an entire L</file> into a L</string> in one operation.

=item socket

An endpoint for network communication among multiple
L<processes|/process> that works much like a telephone or a post
office box.  The most important thing about a socket is its L</network
address> (like a phone number).  Different kinds of sockets have
different kinds of addresses--some look like filenames, and some
don't.

=item soft reference

See L</symbolic reference>.

=item source filter

A special kind of L</module> that does L</preprocessing> on your
script just before it gets to the L</tokener>.

=item stack

A device you can put things on the top of, and later take them back
off in the opposite order in which you put them on.  See L</LIFO>.

=item standard

Included in the official Perl distribution, as in a standard module, a
standard tool, or a standard Perl L</manpage>.

=item standard error

The default output L</stream> for nasty remarks that don't belong in
L</standard output>.  Represented within a Perl program by the
L</filehandle> L</STDERR>.  You can use this stream explicitly, but the
L<die|perlfunc/die> and L<warn|perlfunc/warn> built-ins write to your
standard error stream automatically.

=item standard I/O

A standard C library for doing L<buffered|/buffer> input and output to
the L</operating system>.  (The "standard" of standard I/O is only
marginally related to the "standard" of standard input and output.)
In general, Perl relies on whatever implementation of standard I/O a
given operating system supplies, so the buffering characteristics of a
Perl program on one machine may not exactly match those on another
machine.  Normally this only influences efficiency, not semantics.  If
your standard I/O package is doing block buffering and you want it to
L</flush> the buffer more often, just set the C<$|> variable to a true
value.

=item standard input

The default input L</stream> for your program, which if possible
shouldn't care where its data is coming from.  Represented within a
Perl program by the L</filehandle> L</STDIN>.

=item standard output

The default output L</stream> for your program, which if possible
shouldn't care where its data is going.  Represented within a Perl
program by the L</filehandle> L</STDOUT>.

=item stat structure

A special internal spot in which Perl keeps the information about the
last L</file> on which you requested information.

=item statement

A L</command> to the computer about what to do next, like a step in a
recipe: "Add marmalade to batter and mix until mixed."  A statement is
distinguished from a L</declaration>, which doesn't tell the computer
to do anything, but just to learn something.

=item statement modifier

A L</conditional> or L</loop> that you put after the L</statement>
instead of before, if you know what we mean.

=item static

Varying slowly compared to something else.  (Unfortunately, everything
is relatively stable compared to something else, except for certain
elementary particles, and we're not so sure about them.)  In
computers, where things are supposed to vary rapidly, "static" has a
derogatory connotation, indicating a slightly dysfunctional
L</variable>, L</subroutine>, or L</method>.  In Perl culture, the
word is politely avoided.

=item static method

No such thing.  See L</class method>.

=item static scoping

No such thing.  See L</lexical scoping>.

=item static variable

No such thing.  Just use a L</lexical variable> in a scope larger than
your L</subroutine>.

=item status

The L</value> returned to the parent L</process> when one of its child
processes dies.  This value is placed in the special variable C<$?>.
Its upper eight L<bits|/bit> are the exit status of the defunct
process, and its lower eight bits identify the signal (if any) that
the process died from.  On Unix systems, this status value is the same
as the status word returned by I<wait>(2).  See L<perlfunc/system>.

=item STDERR

See L</standard error>.

=item STDIN

See L</standard input>.

=item STDIO

See L</standard IE<sol>O>.

=item STDOUT

See L</standard output>.

=item stream

A flow of data into or out of a process as a steady sequence of bytes
or characters, without the appearance of being broken up into packets.
This is a kind of L</interface>--the underlying L</implementation> may
well break your data up into separate packets for delivery, but this
is hidden from you.

=item string

A sequence of characters such as "He said !@#*&%@#*?!".  A string does
not have to be entirely printable.

=item string context

The situation in which an expression is expected by its surroundings
(the code calling it) to return a L</string>.  See also L</context>
and L</numeric context>.

=item stringification

The process of producing a L</string> representation of an abstract
object.

=item struct

C keyword introducing a structure definition or name.

=item structure

See L</data structure>.

=item subclass

See L</derived class>.

=item subpattern

A component of a L</regular expression> pattern.

=item subroutine

A named or otherwise accessible piece of program that can be invoked
from elsewhere in the program in order to accomplish some sub-goal of
the program.  A subroutine is often parameterized to accomplish
different but related things depending on its input
L<arguments|/argument>.  If the subroutine returns a meaningful
L</value>, it is also called a L</function>.

=item subscript

A L</value> that indicates the position of a particular L</array>
L</element> in an array.

=item substitution

Changing parts of a string via the C<s///> operator.  (We avoid use of
this term to mean L</variable interpolation>.)

=item substring

A portion of a L</string>, starting at a certain L</character>
position (L</offset>) and proceeding for a certain number of
characters.

=item superclass

See L</base class>.

=item superuser

The person whom the L</operating system> will let do almost anything.
Typically your system administrator or someone pretending to be your
system administrator.  On Unix systems, the L</root> user.  On Windows
systems, usually the Administrator user.

=item SV

Short for "scalar value".  But within the Perl interpreter every
L</referent> is treated as a member of a class derived from SV, in an
object-oriented sort of way.  Every L</value> inside Perl is passed
around as a C language C<SV*> pointer.  The SV L</struct> knows its
own "referent type", and the code is smart enough (we hope) not to try
to call a L</hash> function on a L</subroutine>.

=item switch

An option you give on a command line to influence the way your program
works, usually introduced with a minus sign.  The word is also used as
a nickname for a L</switch statement>.

=item switch cluster

The combination of multiple command-line switches (e.g., B<-a -b -c>)
into one switch (e.g., B<-abc>).  Any switch with an additional
L</argument> must be the last switch in a cluster.

=item switch statement

A program technique that lets you evaluate an L</expression> and then,
based on the value of the expression, do a multiway branch to the
appropriate piece of code for that value.  Also called a "case
structure", named after the similar Pascal construct.  See
L<perlsyn/"Switch statements">.

=item symbol

Generally, any L</token> or L</metasymbol>.  Often used more
specifically to mean the sort of name you might find in a L</symbol
table>.

=item symbol table

Where a L</compiler> remembers symbols.  A program like Perl must
somehow remember all the names of all the L<variables|/variable>,
L<filehandles|/filehandle>, and L<subroutines|/subroutine> you've
used.  It does this by placing the names in a symbol table, which is
implemented in Perl using a L</hash table>.  There is a separate
symbol table for each L</package> to give each package its own
L</namespace>.

=item symbolic debugger

A program that lets you step through the L<execution|/execute> of your
program, stopping or printing things out here and there to see whether
anything has gone wrong, and if so, what.  The "symbolic" part just
means that you can talk to the debugger using the same symbols with
which your program is written.

=item symbolic link

An alternate filename that points to the real L</filename>, which in
turn points to the real L</file>.  Whenever the L</operating system>
is trying to parse a L</pathname> containing a symbolic link, it
merely substitutes the new name and continues parsing.

=item symbolic reference

A variable whose value is the name of another variable or subroutine.
By L<dereferencing|/dereference> the first variable, you can get at
the second one.  Symbolic references are illegal under L<use strict
'refs'|strict/strict refs>.

=item synchronous

Programming in which the orderly sequence of events can be determined;
that is, when things happen one after the other, not at the same time.

=item syntactic sugar

An alternative way of writing something more easily; a shortcut.

=item syntax

From Greek, "with-arrangement".  How things (particularly symbols) are
put together with each other.

=item syntax tree

An internal representation of your program wherein lower-level
L<constructs|/construct> dangle off the higher-level constructs
enclosing them.

=item syscall

A L</function> call directly to the L</operating system>.  Many of the
important subroutines and functions you use aren't direct system
calls, but are built up in one or more layers above the system call
level.  In general, Perl programmers don't need to worry about the
distinction.  However, if you do happen to know which Perl functions
are really syscalls, you can predict which of these will set the C<$!>
(C<$ERRNO>) variable on failure.  Unfortunately, beginning programmers
often confusingly employ the term "system call" to mean what happens
when you call the Perl L<system|perlfunc/system> function, which
actually involves many syscalls.  To avoid any confusion, we nearly
always use say "syscall" for something you could call indirectly via
Perl's L<syscall|perlfunc/syscall> function, and never for something
you would call with Perl's L<system|perlfunc/system> function.

=back

=head2 T

=over 4

=item tainted

Said of data derived from the grubby hands of a user and thus unsafe
for a secure program to rely on.  Perl does taint checks if you run a
L</setuid> (or L</setgid>) program, or if you use the B<-T> switch.

=item TCP

Short for Transmission Control Protocol.  A protocol wrapped around
the Internet Protocol to make an unreliable packet transmission
mechanism appear to the application program to be a reliable
L</stream> of bytes.  (Usually.)

=item term

Short for a "terminal", that is, a leaf node of a L</syntax tree>.  A
thing that functions grammatically as an L</operand> for the operators
in an expression.

=item terminator

A L</character> or L</string> that marks the end of another string.
The C<$/> variable contains the string that terminates a
L<readline|perlfunc/readline> operation, which L<chomp|perlfunc/chomp>
deletes from the end.  Not to be confused with
L<delimiters|/delimiter> or L<separators|/separator>.  The period at
the end of this sentence is a terminator.

=item ternary

An L</operator> taking three L<operands|/operand>.  Sometimes
pronounced L</trinary>.

=item text

A L</string> or L</file> containing primarily printable characters.

=item thread

Like a forked process, but without L</fork>'s inherent memory
protection.  A thread is lighter weight than a full process, in that a
process could have multiple threads running around in it, all fighting
over the same process's memory space unless steps are taken to protect
threads from each other.  See L<threads>.

=item tie

The bond between a magical variable and its implementation class.  See
L<perlfunc/tie> and L<perltie>.

=item TMTOWTDI

There's More Than One Way To Do It, the Perl Motto.  The notion that
there can be more than one valid path to solving a programming problem
in context.  (This doesn't mean that more ways are always better or
that all possible paths are equally desirable--just that there need
not be One True Way.)  Pronounced TimToady.

=item token

A morpheme in a programming language, the smallest unit of text with
semantic significance.

=item tokener

A module that breaks a program text into a sequence of
L<tokens|/token> for later analysis by a parser.

=item tokenizing

Splitting up a program text into L<tokens|/token>.  Also known as
"lexing", in which case you get "lexemes" instead of tokens.

=item toolbox approach

The notion that, with a complete set of simple tools that work well
together, you can build almost anything you want.  Which is fine if
you're assembling a tricycle, but if you're building a defranishizing
comboflux regurgalator, you really want your own machine shop in which
to build special tools.  Perl is sort of a machine shop.

=item transliterate

To turn one string representation into another by mapping each
character of the source string to its corresponding character in the
result string.  See
L<perlop/trE<sol>SEARCHLISTE<sol>REPLACEMENTLISTE<sol>cdsr>.

=item trigger

An event that causes a L</handler> to be run.

=item trinary

Not a stellar system with three stars, but an L</operator> taking
three L<operands|/operand>.  Sometimes pronounced L</ternary>.

=item troff

A venerable typesetting language from which Perl derives the name of
its C<$%> variable and which is secretly used in the production of
Camel books.

=item true

Any scalar value that doesn't evaluate to 0 or C<"">.

=item truncating

Emptying a file of existing contents, either automatically when
opening a file for writing or explicitly via the
L<truncate|perlfunc/truncate> function.

=item type

See L</data type> and L</class>.

=item type casting

Converting data from one type to another.  C permits this.  Perl does
not need it.  Nor want it.

=item typed lexical

A L</lexical variable> that is declared with a L</class> type: C<my
Pony $bill>.

=item typedef

A type definition in the C language.

=item typeglob

Use of a single identifier, prefixed with C<*>.  For example, C<*name>
stands for any or all of C<$name>, C<@name>, C<%name>, C<&name>, or
just C<name>.  How you use it determines whether it is interpreted as
all or only one of them.  See L<perldata/Typeglobs and Filehandles>.

=item typemap

A description of how C types may be transformed to and from Perl types
within an L</extension> module written in L</XS>.

=back

=head2 U

=over 4

=item UDP

User Datagram Protocol, the typical way to send L<datagrams|/datagram>
over the Internet.

=item UID

A user ID.  Often used in the context of L</file> or L</process>
ownership.

=item umask

A mask of those L</permission bits> that should be forced off when
creating files or directories, in order to establish a policy of whom
you'll ordinarily deny access to.  See the L<umask|perlfunc/umask>
function.

=item unary operator

An operator with only one L</operand>, like C<!> or
L<chdir|perlfunc/chdir>.  Unary operators are usually prefix
operators; that is, they precede their operand.  The C<++> and C<-->
operators can be either prefix or postfix.  (Their position I<does>
change their meanings.)

=item Unicode

A character set comprising all the major character sets of the world,
more or less.  See L<perlunicode> and L<http://www.unicode.org>.

=item Unix

A very large and constantly evolving language with several alternative
and largely incompatible syntaxes, in which anyone can define anything
any way they choose, and usually do.  Speakers of this language think
it's easy to learn because it's so easily twisted to one's own ends,
but dialectical differences make tribal intercommunication nearly
impossible, and travelers are often reduced to a pidgin-like subset of
the language.  To be universally understood, a Unix shell programmer
must spend years of study in the art.  Many have abandoned this
discipline and now communicate via an Esperanto-like language called
Perl.

In ancient times, Unix was also used to refer to some code that a
couple of people at Bell Labs wrote to make use of a PDP-7 computer
that wasn't doing much of anything else at the time.

=back

=head2 V

=over 4

=item value

An actual piece of data, in contrast to all the variables, references,
keys, indexes, operators, and whatnot that you need to access the
value.

=item variable

A named storage location that can hold any of various kinds of
L</value>, as your program sees fit.

=item variable interpolation

The L</interpolation> of a scalar or array variable into a string.

=item variadic

Said of a L</function> that happily receives an indeterminate number
of L</actual arguments>.

=item vector

Mathematical jargon for a list of L<scalar values|/scalar value>.

=item virtual

Providing the appearance of something without the reality, as in:
virtual memory is not real memory.  (See also L</memory>.)  The
opposite of "virtual" is "transparent", which means providing the
reality of something without the appearance, as in: Perl handles the
variable-length UTF-8 character encoding transparently.

=item void context

A form of L</scalar context> in which an L</expression> is not
expected to return any L</value> at all and is evaluated for its
L</side effects> alone.

=item v-string

A "version" or "vector" L</string> specified with a C<v> followed by a
series of decimal integers in dot notation, for instance,
C<v1.20.300.4000>.  Each number turns into a L</character> with the
specified ordinal value.  (The C<v> is optional when there are at
least three integers.)

=back

=head2 W

=over 4

=item warning

A message printed to the L</STDERR> stream to the effect that something
might be wrong but isn't worth blowing up over.  See L<perlfunc/warn>
and the L<warnings> pragma.

=item watch expression

An expression which, when its value changes, causes a breakpoint in
the Perl debugger.

=item whitespace

A L</character> that moves your cursor but doesn't otherwise put
anything on your screen.  Typically refers to any of: space, tab, line
feed, carriage return, or form feed.

=item word

In normal "computerese", the piece of data of the size most
efficiently handled by your computer, typically 32 bits or so, give or
take a few powers of 2.  In Perl culture, it more often refers to an
alphanumeric L</identifier> (including underscores), or to a string of
nonwhitespace L<characters|/character> bounded by whitespace or string
boundaries.

=item working directory

Your current L</directory>, from which relative pathnames are
interpreted by the L</operating system>.  The operating system knows
your current directory because you told it with a
L<chdir|perlfunc/chdir> or because you started out in the place where
your parent L</process> was when you were born.

=item wrapper

A program or subroutine that runs some other program or subroutine for
you, modifying some of its input or output to better suit your
purposes.

=item WYSIWYG

What You See Is What You Get.  Usually used when something that
appears on the screen matches how it will eventually look, like Perl's
L<format|perlfunc/format> declarations.  Also used to mean the
opposite of magic because everything works exactly as it appears, as
in the three-argument form of L<open|perlfunc/open>.

=back

=head2 X

=over 4

=item XS

An extraordinarily exported, expeditiously excellent, expressly
eXternal Subroutine, executed in existing C or C++ or in an exciting
new extension language called (exasperatingly) XS.  Examine L<perlxs>
for the exact explanation or L<perlxstut> for an exemplary unexacting
one.

=item XSUB

An external L</subroutine> defined in L</XS>.

=back

=head2 Y

=over 4

=item yacc

Yet Another Compiler Compiler.  A parser generator without which Perl
probably would not have existed.  See the file I<perly.y> in the Perl
source distribution.

=back

=head2 Z

=over 4

=item zero width

A subpattern L</assertion> matching the L</null string> between
L<characters|/character>.

=item zombie

A process that has died (exited) but whose parent has not yet received
proper notification of its demise by virtue of having called
L<wait|perlfunc/wait> or L<waitpid|perlfunc/waitpid>.  If you
L<fork|perlfunc/fork>, you must clean up after your child processes
when they exit, or else the process table will fill up and your system
administrator will Not Be Happy with you.

=back

=head1 AUTHOR AND COPYRIGHT

Based on the Glossary of Programming Perl, Third Edition,
by Larry Wall, Tom Christiansen & Jon Orwant.
Copyright (c) 2000, 1996, 1991 O'Reilly Media, Inc.
This document may be distributed under the same terms as Perl itself.