-s   enables rudimentary switch parsing for switches on
            the command line after the program name but before
            any filename arguments (or before a --).  Any switch
            found there is removed from @ARGV and sets the
            corresponding variable in the Perl program.  The
            following program prints "1" if the program is
            invoked with a -xyz switch, and "abc" if it is
            invoked with -xyz=abc.

                #!/usr/bin/perl -s
                if ($xyz) { print "$xyz\n" }