weak references. This module is a Perl-level interface to that API,
allowing weak references to be created in Perl.
A weak reference is just like an ordinary Perl reference except
that it isn't included in the reference count of the thing referred
to. This means that once all references to a particular piece of
data are weak, the piece of data is freed and all the weak references
are set to undef. This is particularly useful for implementing
circular data structures without memory leaks or caches of objects.
WWW: http://search.cpan.org/dist/WeakRef/
PR: ports/98963
Submitted by: Dmitry Marakasov <amdmi3@mail.ru>
