Test::Deep gives you very flexible ways to check that the result you
got is the result you were expecting. At it's simplest it compares two
structures by going through each level, ensuring that the values
match, that arrays and hashes have the same elements and that
references are blessed into the correct class. It also handles
circular data structures without getting caught in an infinite loop.

WWW: http://search.cpan.org/dist/Test-Deep/