/usr/share/acl2-6.3/books/str/ is in acl2-books-source 6.3-5.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-6.3/books/str/abbrevs.lisp
/usr/share/acl2-6.3/books/str/arithmetic.lisp
/usr/share/acl2-6.3/books/str/base64.acl2
/usr/share/acl2-6.3/books/str/base64.lisp
/usr/share/acl2-6.3/books/str/case-conversion.lisp
/usr/share/acl2-6.3/books/str/cat.lisp
/usr/share/acl2-6.3/books/str/cert.acl2
/usr/share/acl2-6.3/books/str/char-case.lisp
/usr/share/acl2-6.3/books/str/char-fix.lisp
/usr/share/acl2-6.3/books/str/coerce.lisp
/usr/share/acl2-6.3/books/str/defs.lisp
/usr/share/acl2-6.3/books/str/digitp.lisp
/usr/share/acl2-6.3/books/str/eqv.lisp
/usr/share/acl2-6.3/books/str/explode-atom.lisp
/usr/share/acl2-6.3/books/str/explode-nonnegative-integer.lisp
/usr/share/acl2-6.3/books/str/fast-cat.acl2
/usr/share/acl2-6.3/books/str/fast-cat.lisp
/usr/share/acl2-6.3/books/str/firstn-chars.lisp
/usr/share/acl2-6.3/books/str/hexify.lisp
/usr/share/acl2-6.3/books/str/html-encode.lisp
/usr/share/acl2-6.3/books/str/ieqv.lisp
/usr/share/acl2-6.3/books/str/iless.lisp
/usr/share/acl2-6.3/books/str/iprefixp.lisp
/usr/share/acl2-6.3/books/str/isort.lisp
/usr/share/acl2-6.3/books/str/istrpos.lisp
/usr/share/acl2-6.3/books/str/istrprefixp.lisp
/usr/share/acl2-6.3/books/str/isubstrp.lisp
/usr/share/acl2-6.3/books/str/make-character-list.lisp
/usr/share/acl2-6.3/books/str/match/
/usr/share/acl2-6.3/books/str/match/cert.acl2
/usr/share/acl2-6.3/books/str/natstr.lisp
/usr/share/acl2-6.3/books/str/pad.lisp
/usr/share/acl2-6.3/books/str/portcullis.acl2
/usr/share/acl2-6.3/books/str/portcullis.lisp
/usr/share/acl2-6.3/books/str/prefix-lines.lisp
/usr/share/acl2-6.3/books/str/stringify.lisp
/usr/share/acl2-6.3/books/str/strline.lisp
/usr/share/acl2-6.3/books/str/strnatless.lisp
/usr/share/acl2-6.3/books/str/strpos.lisp
/usr/share/acl2-6.3/books/str/strprefixp.lisp
/usr/share/acl2-6.3/books/str/strrpos.lisp
/usr/share/acl2-6.3/books/str/strsplit.lisp
/usr/share/acl2-6.3/books/str/strsubst.lisp
/usr/share/acl2-6.3/books/str/strtok.lisp
/usr/share/acl2-6.3/books/str/strval.lisp
/usr/share/acl2-6.3/books/str/subseq.lisp
/usr/share/acl2-6.3/books/str/substrp.lisp
/usr/share/acl2-6.3/books/str/suffixp.lisp
/usr/share/acl2-6.3/books/str/symbols.lisp
/usr/share/acl2-6.3/books/str/top.lisp