/usr/share/javascript/prettify/lang-erlang.js is in libjs-prettify 2013.03.04+dfsg-4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | PR.registerLangHandler(PR.createSimpleLexer([["pln",/^[\t\n\x0B\x0C\r ]+/,null,"\t\n\x0B\f\r "],["str",/^\"(?:[^\"\\\n\x0C\r]|\\[\s\S])*(?:\"|$)/,null,'"'],["lit",/^[a-z][a-zA-Z0-9_]*/],["lit",/^\'(?:[^\'\\\n\x0C\r]|\\[^&])+\'?/,null,"'"],["lit",/^\?[^ \t\n({]+/,null,"?"],["lit",/^(?:0o[0-7]+|0x[\da-f]+|\d+(?:\.\d+)?(?:e[+\-]?\d+)?)/i,null,"0123456789"]],[["com",/^%[^\n]*/],["kwd",/^(?:module|attributes|do|let|in|letrec|apply|call|primop|case|of|end|when|fun|try|catch|receive|after|char|integer|float,atom,string,var)\b/],
["kwd",/^-[a-z_]+/],["typ",/^[A-Z_][a-zA-Z0-9_]*/],["pun",/^[.,;]/]]),["erlang","erl"]);
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