use CGI::Session;
use CGI;

#set up a session
$cgi = CGI->new;
$session = CGI::Session->new("driver:File", $cgi, {Directory=>"./tmp"});
$sid = $session->id();

$cookie = $cgi->cookie(CGISESSID => $session->id);
print $cgi->header( -cookie=>$cookie );
$sid = $cgi->cookie("CGISESSID") || undef;
$session = new CGI::Session(undef, $sid, {Directory=>'/tmp'});