Path to plugin class from a Twig_Node
Assuming PluginCustomClass is a class inside of a Craft plugin, then the issue is probably that you need to reference it in the Craft namespace.  Something like this should work:

-&gt;raw(') = new \Craft\PluginCustomClass(')


Depending on what type of class that is (Service, Variable, Helper, standalone, etc.), Craft might not have auto-loaded it, so you might need to manually require it as well.