perldoc > chmod

    chmod LIST
            Changes the permissions of a list of files. The first element of
            the list must be the numeric mode, which should probably be an
            octal number, and which definitely should *not* be a string of
            octal digits: 0644 is okay, but "0644" is not. Returns the
            number of files successfully changed. See also "oct" if all you
            have is a string.

                my $cnt = chmod 0755, "foo", "bar";
                chmod 0755, @executables;
                my $mode = "0644"; chmod $mode, "foo";      # !!! sets mode to
                                                            # --w----r-T
                my $mode = "0644"; chmod oct($mode), "foo"; # this is better
                my $mode = 0644;   chmod $mode, "foo";      # this is best

            On systems that support fchmod(2), you may pass filehandles
            among the files. On systems that don't support fchmod(2),
            passing filehandles raises an exception. Filehandles must be
            passed as globs or glob references to be recognized; barewords
            are considered filenames.

                open(my $fh, "<", "foo");
                my $perm = (stat $fh)[2] & 07777;
                chmod($perm | 0600, $fh);

            You can also import the symbolic "S_I*" constants from the
            "Fcntl" module:

                use Fcntl qw( :mode );
                chmod S_IRWXU|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH, @executables;
                # Identical to the chmod 0755 of the example above.

            Portability issues: "chmod" in perlport.