adrianh, have you found some good material on TDD in Perl? I'm finding TDD, so far, only slightly less painful than debugging :-) . (Though I just received Kent Beck's book today, so maybe I'll pick up some wisdom there.)

There's not a huge amount available specifically on developing perl in a TDD manner. There's Rob Nagler's Extreme Perl, Peter Scott talks about it a little in Perl Medic and I believe that there's a bit on TDD in TheDamian's new book.

But really there is nothing language-specific about TDD so I'd recommend reading Kent's book and taking it from there.