/usr/share/acl2-7.1/books/std/strings/ is in acl2-books 7.1-1.
This file is owned by root:root, with mode 0o755.
..
/usr/share/acl2-7.1/books/std/strings/abbrevs.o
/usr/share/acl2-7.1/books/std/strings/arithmetic.o
/usr/share/acl2-7.1/books/std/strings/base64.o
/usr/share/acl2-7.1/books/std/strings/binary.o
/usr/share/acl2-7.1/books/std/strings/case-conversion.o
/usr/share/acl2-7.1/books/std/strings/cat.o
/usr/share/acl2-7.1/books/std/strings/char-case.o
/usr/share/acl2-7.1/books/std/strings/char-fix.o
/usr/share/acl2-7.1/books/std/strings/charset-fns.o
/usr/share/acl2-7.1/books/std/strings/charset.o
/usr/share/acl2-7.1/books/std/strings/coerce.o
/usr/share/acl2-7.1/books/std/strings/decimal.o
/usr/share/acl2-7.1/books/std/strings/defs-aux.o
/usr/share/acl2-7.1/books/std/strings/defs-program.o
/usr/share/acl2-7.1/books/std/strings/defs.o
/usr/share/acl2-7.1/books/std/strings/eqv.o
/usr/share/acl2-7.1/books/std/strings/explode-atom.o
/usr/share/acl2-7.1/books/std/strings/explode-nonnegative-integer.o
/usr/share/acl2-7.1/books/std/strings/fast-cat-raw.o
/usr/share/acl2-7.1/books/std/strings/fast-cat.o
/usr/share/acl2-7.1/books/std/strings/firstn-chars.o
/usr/share/acl2-7.1/books/std/strings/hex.o
/usr/share/acl2-7.1/books/std/strings/hexify.o
/usr/share/acl2-7.1/books/std/strings/html-encode.o
/usr/share/acl2-7.1/books/std/strings/ieqv.o
/usr/share/acl2-7.1/books/std/strings/iless.o
/usr/share/acl2-7.1/books/std/strings/iprefixp.o
/usr/share/acl2-7.1/books/std/strings/isort.o
/usr/share/acl2-7.1/books/std/strings/istrpos.o
/usr/share/acl2-7.1/books/std/strings/istrprefixp.o
/usr/share/acl2-7.1/books/std/strings/isubstrp.o
/usr/share/acl2-7.1/books/std/strings/make-character-list.o
/usr/share/acl2-7.1/books/std/strings/octal.o
/usr/share/acl2-7.1/books/std/strings/pad.o
/usr/share/acl2-7.1/books/std/strings/prefix-lines.o
/usr/share/acl2-7.1/books/std/strings/pretty-defs-aux.o
/usr/share/acl2-7.1/books/std/strings/pretty-defs.o
/usr/share/acl2-7.1/books/std/strings/pretty-program.o
/usr/share/acl2-7.1/books/std/strings/pretty-tests.o
/usr/share/acl2-7.1/books/std/strings/pretty.o
/usr/share/acl2-7.1/books/std/strings/stringify.o
/usr/share/acl2-7.1/books/std/strings/strline.o
/usr/share/acl2-7.1/books/std/strings/strnatless.o
/usr/share/acl2-7.1/books/std/strings/strpos.o
/usr/share/acl2-7.1/books/std/strings/strprefixp.o
/usr/share/acl2-7.1/books/std/strings/strrpos.o
/usr/share/acl2-7.1/books/std/strings/strsplit.o
/usr/share/acl2-7.1/books/std/strings/strsubst.o
/usr/share/acl2-7.1/books/std/strings/strtok.o
/usr/share/acl2-7.1/books/std/strings/subseq.o
/usr/share/acl2-7.1/books/std/strings/substrp.o
/usr/share/acl2-7.1/books/std/strings/suffixp.o
/usr/share/acl2-7.1/books/std/strings/symbols.o
/usr/share/acl2-7.1/books/std/strings/top.o