test module that asserts the referential identity of a reference

 Test::Identity provides a single testing function, identical. It asserts that
 a given reference is as expected; that is, it either refers to the same
 object or is undef. It is similar to Test::More::is except that it uses
 refaddr, ensuring that it behaves correctly even if the references under test
 are objects that overload stringification or numification. It also provides
 better diagnostics if the test fails.