12.11. Modifying Permissions
chmod 0755, "fred", "barney";
As with many of the operating system interface functions, chmod returns the number of items successfully altered and, when used with a single argument, sets $! in a sensible way for error messages when it fails. The first parameter is the Unix permission value (even for non-Unix versions of Perl). For the same reasons we presented earlier in describing mkdir, this value is usually specified in octal.
Symbolic permissions (like +x or go=u-w) accepted by the Unix chmod command are not valid for the chmod function.[*]