This is my first attempt at TDD in Perl. I'm using Test::Simple and nothing more complicated than ok.

The Test-Simple distribution includes the Test::More module - since you already have it installed, you might as well use it. For an example of how this will improve your life, consider this test:

ok(animal() eq 'monkey', 'animal() returned monkey')
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Using the is function from Test::More the same test might be written like this:

is(animal(), 'monkey', 'check animal() return value')
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The difference is that when your test fails, the diagnostic output will tell you what value was expected and what was actually received - making things much easier to debug.

Test::More has a number of handy functions like this which will save your time.