Some times ago I wrote same script and one good brother in perl help me with this. So now try to help you...

He re is part of my program:

use CGI;
$query = new CGI;

sub logout {
    $cookie_expires = "-1s";
    &cookie_create;
    print $query->redirect( -uri => $redirect_to, -cookie => $cookie )
+;
}

sub cookie_create {
    $cookie = $query->cookie(-name => $cookie_name,
                              -expires => $cookie_expires,
                              -domain  => $cookie_domain,
                              -path    => $cookie_path,
                              -value=>{ username => $username,
                                      password => crypt($password, $us
+ername) }
                               );
}
[download]

As you can see cookie_create sub can be also used to create cookie not only to erase it. This worked well, if you want all script which verify login again csv flat file user database I can send it to you.

Good luck

Li Tin O've Weedle
mad Tsort's philosopher