##########################################################
## THIS PROCEDURE MAKES SURE THAT THE USER IS LOGGED IN
##########################################################
sub CheckIfUserIsLoggedIn
{

use CGI::Session;
my ($sid,$session,$userid);

$cgi=new CGI;
$sid=$cgi->cookie("CGISESSID")||undef;
$session = new CGI::Session("driver:DB_File",$sid,{Directory=>'/tmp'});
$userid = $session->param("userid");

if ($userid eq "")
{
print "Content-type: text/html\n\n";
print "You are not logged in!! $userid\n\n";
exit;
}
else
{
        return $userid;
}
}
####################################################



The code below is from the login.pl routine that sets the cookie after checking that the password and username match what is in the DB:

        ## If the username and password are correct, then set cookie and proceed
        if ($r[0] eq $psswd)
        {
                $cgi = new CGI;
                $session = new CGI::Session("driver:DB_File",undef,{Directory=>'/tmp'});
                $sid=$session->id();
                $session->param("userid",$r[1]);
                $cookie=$cgi->cookie(CGISESSID=>$session->id);
                print $cgi->header(-cookie=>$cookie);
                $sesname=$session->param("userid");
                $content = &Get_Account_Manager_html($r[1],$r[2],$r[3]); ## we pass the userid
                $content = "<b>userid:$sesname</b>".$content;
                &PrintWebpage($content,"yes");
        }