sub vcl_hash {
    hash_data(req.url);

    if (req.http.host) {
        hash_data(req.http.host);
    } else {
        hash_data(server.ip);
    }

    if(req.http.Cookie ~ "Foobar=") {
        hash_data(regsub(req.http.Cookie, '.*(Foobar=[^;]+).*'));
    }

    return (lookup);
}