Curnode is a GroovyNode object. The GroovyNode class is a convenience class that wraps JsonNode. It is only available in submappers and their filters, and it holds the data that was selected by its parent mapper. The curnode is not a message, but its data can be accessed in the same way. Persistence works slightly different in curnode. To persist a curnode, first you need to set an id. Then you can call functions similar to message functions such as previous() and changed(key). At the end of the script, you need to explicitly save the node to the database by calling curnode.save().
Sample code:
curnode.setId(curnode.label)
curnode.put("changed",curnode.changed("display"))
curnode.put("groovy","right on")
curnode.save()