use Perl

While working on Math::Interval I wrote a few tests to validate that everything was working correctly. After fixing my typos in the .t files I was delighted to discover a few errors in my code. I say I was delighted because it was much easier to track them down now than later.

As a bonus using Devel::Cover I have a nicely formatted report that shows the code that was missed by my testing so that I can add a few more tests to make sure that all code paths are correct.

Thank you everyone who wrote these modules!