You also might want to take a look at Test::Cmd, which I created to try to factor out some underlying testing building blocks common to a number of utilities for which I was writing test suites. The intention is for you to subclass Test::Cmd to build up testing infrastructure that's particular to your command or system under test.

In addition to providing some potentially useful testing infrastructure in its own right, it uses the standard Test module for its own internal tests, which might serve as a useful example.