'Test::Weaken' helps detect unfreed Perl data in arrays, hashes, scalars,
objects, etc, by descending recursively through structures and watching
that everything is freed. Unfreed data is a useless overhead and may cause
an application to abend due to lack of memory.

Normally if the last reference to something is discarded then it and
anything in it is freed automatically. But this might not occur due to
circular references, unexpected global variables or closures, or reference
counting mistakes in XSUBs.

'Test::Weaken' is named for the strategy used to detect leaks. References
are taken to the test objects and all their contents, then those references
are weakened and expected to be then freed.