use strict;
use warnings;
use Getopt::Long;


GetOptions(
           'demo' => \&demo,
           'test' => \&test
          )
  or die("Error in command line arguments\n");


sub demo {
    my ( $arg0, $arg1, $arg2, $arg3, $arg4, $arg5 ) = @_ ;
    warn "Number of args: ", scalar @_;
    die "expected 2 args" if @_ != 2;
    warn join ",",@_;
}

sub test {
    die "expected 2 args" if @_ != 2;
	warn join ",",@_;
	demo("hello", "world");
}

##</code><code>##

test,1 at d:/tmp/pm/getopt_long.pl line 23, <DATA> line 26.
Number of args: 2 at d:/tmp/pm/getopt_long.pl line 16, <DATA> line 26.
hello,world at d:/tmp/pm/getopt_long.pl line 18, <DATA> line 26.