public function flushExpression() {
        $args = func_get_args();
        $result = array();
        foreach (Mage::helper('turpentine/varnish')->getSockets() as $socket) {
            $socketName = $socket->getConnectionString();
            try {
                call_user_func_array(array($socket, 'ban'), $args);
            } catch (Mage_Core_Exception $e) {
                $result[$socketName] = $e->getMessage();
                continue;
            }
            $result[$socketName] = true;
        }
        return $result;
    }