public function checkCacheFlag($eventObject) {
        if (Mage::helper('turpentine/varnish')->shouldResponseUseVarnish()) {
            $layoutXml = $eventObject->getLayout()->getUpdate()->asSimplexml();
            foreach ($layoutXml->xpath('//turpentine_cache_flag') as $node) {
                foreach ($node->attributes() as $attr => $value) {
                    if ($attr == 'value') {
                        if ( ! (string) $value) {
                            Mage::register('turpentine_nocache_flag', true, true);
                            return; //only need to set the flag once
                        }
                    }
                }
            }
        }
    }