Writing table-driven tests is usually a good idea. Adding a test case doesn't
require adding code, so it's easy to avoid fucking up the other tests. However,
actually going from a table of tests to a test that runs is non-trivial.

Test::TableDriven makes writing the test drivers trivial. You simply define your
test cases and write a function that turns the input data into output data to
compare against. Test::TableDriven will compute how many tests need to be run,
and then run the tests.

Concentrate on your data and what you're testing, not plan tests = scalar keys
%test_cases> and a big foreach loop.