Thanks to Henrik for clearing up my previous problem, my bad. I have it working now.
My next hurdle is that I have lots of information that I'd like to graph from a single test that won't graph well together... Some values are always in the single digits, some values are in the many thousands. Can I get more than one graph definition to display under the test?
The other option I thought of is populating a different graph for each value and using @RRDFN@, but I don't see a good way to group the results in a meaningfull way.