#  $sid = '7032f2c7f5a2c721a483dc75fc29595e';
  $session = new CGI::Session("driver:MySQL", $sid, {Handle=>$dbh});

##</code><code>##

#!/usr/bin/perl
use strict; use warnings; 


select STDOUT; $| = 1;

use CGI;

use CGI::Session;
my $existn=0; 

my $sid=make_first(); 
sleep 10; find_if_exist ($sid); 
sleep 20; find_if_exist ($sid); 
find_if_exist('abcd'); 
exit; 

sub make_first {
my $session = new CGI::Session(undef, undef, {Directory=>'.'});

my $sid=$session->id; 

$session->expires('+15s');
$session->param('user_id',time);
$session->flush();
return $sid; 
} 


sub find_if_exist {
my $sid0=shift; 
$existn++; 
print '******Exist call:'.$existn."\n"; 
my $session = new CGI::Session(undef, $sid0, {Directory=>'.'});

my $sid=$session->id; 
my $user=$session->param('user_id'); 
unless (defined $user) {$user='undef-as-string'; } 
unless ($sid0 eq $sid) {print "********different   "; } 
print 'sid0:'.$sid0.' sid:'.$sid."\n"; 
print 'user:'.$user."\n\n";
} 


##</code><code>##

******Exist call:1
sid0:2bd4a7c8d0001e49e97dc332d6bf619e sid:2bd4a7c8d0001e49e97dc332d6bf619e
user:1491953482

******Exist call:2
********different   sid0:2bd4a7c8d0001e49e97dc332d6bf619e sid:bcd0c39467ce09c5b5be9910f9e1798b
user:undef-as-string

******Exist call:3
********different   sid0:abcd sid:2dd5bc5bc5e297150b1e4c7f58166135
user:undef-as-string