Pretty useful module. I often find myself writing can_ok and isa_ok tests for everything in my app. This module will automate that testing by accepting a quick textual description of what your app's API should look like and seeing if your classes live up to the spec.
XP advocates should like this, since it makes writing the basic use ok, isa_ok, and can_ok tests trivial. One more reason to use Perl instead of Java for agile/XP :)