Description:

The the Tie::RefHash manpage module can be used to access hashes by
reference. This is useful when you index by object, for example.

The problem with the Tie::RefHash manpage, and cross indexing, is that
sometimes the index should not contain strong references to the objecs. the
Tie::RefHash manpage's internal structures contain strong references to the
key, and provide no convenient means to make those references weak.

This subclass of the Tie::RefHash manpage has weak keys, instead of strong
ones. The values are left unaltered, and you'll have to make sure there are
no strong references there yourself.