#test1.pl

#!/usr/bin/perl

use strict;
use warnings;
use CGI;
use CGI::Session qw/-ip-match/;

# instantiate a new CGI object
my $cgi = new CGI;

my $session = new CGI::Session();
my $sessionid = $session->id();

$cgi->param("myname", "max payne");

#save param into session
$session->save_param($cgi);

print "after saving, it's actually : ";
print $session->param("myname");

print $cgi->redirect( -URL     => 'test2.pl?sessionid='.$sessionid);					

##</code><code>##

#test2.pl

#!/usr/bin/perl

use strict;
use warnings;
use CGI;
use CGI::Session qw/-ip-match/;

require "library.pl";

# instantiate a new CGI object
my $cgi = new CGI;
my $sessionid = $cgi->param("sessionid");

	# MARKING 1
	my $session = CGI::Session->load($sessionid);
	
	print "what was my name again >? " . $session->param("myname");
	
	$cgi->param("myname", undef);
	$session->save_param($cgi);
	
	print "<BR>(as undef) what was my name again >? " . $session->param("myname");
	
	$cgi->param("myname", "");
	$session->save_param($cgi);
	
	print "<BR>(as empty string) what was my name again >? " . $session->param("myname");