my $secret_key = "BLAHBLAHBLAH";
        my $session_cookie = $query->cookie('SessionID');
        umask 0066;
        if($session_cookie) {
                my $mac;
                if(($sessionid, $mac) = split("-", $session_cookie)) {
                        ###Ok, the user has returned a cookie,
                        ###let's make sure it's not been tampered with.
                        if($mac ne md5_hex($sessionid . md5_hex($sessionid.$secret_key))) {
                                destroy_cookie($sessionid, "MODIFIED"); ###Ack. Nasty people
                                return;
                        } else {
				###Other checks.
			}