Class::Sniff 0.08_02 will hit the CPAN soon. It has a little command line utility which is an experiment with just easily dumping graphs. I cd'd into my Test::Harness development directory and ran this:
csniff --namespace TAP:: lib/ --png > tap.png
I also tried to recreate the RT inheritance tree. I can't quite load it, but RT has caused some issues in the past. This is the image I got.