#!perl
use strict;
use warnings;
$|++;
my ($comp,$first,@sec);

$comp = "descr is ".(defined $first ? q{$first} : 'null').' and list is '.( @sec ? q{join ' ', @sec} : 'empty');
print "Oringinal:$comp\n";
&modify_first('UNO');
&modify_second (1);&modify_second (2);
&modify_first ('DUE');
&reset_second;


sub modify_first{$first = shift;    print "$comp\n";}
sub modify_second {push @sec, shift; print "$comp\n";}
sub reset_second {@sec=qw();        print "$comp\n";}

__OUTPUT__
Oringinal:descr is null and list is empty
descr is null and list is empty
descr is null and list is empty
descr is null and list is empty
descr is null and list is empty
descr is null and list is empty