This way of associating structs with Perl space objects is designed to supercede
Perl's builtin T_PTROBJ with something that is designed to be:

Extensible

- The association of the pointer using sv_magicext can be done on any data type,
  so you can associate C structs with any representation type.
- This means that you can add pointers to any object (hand coded, Moose or
  otherwise), while still having instance data in regular hashes.

Opaque

- The C pointer is neither visible nor modifiable from Perl space.
- This prevents accidental corruption which could lead to segfaults using
  T_PTROBJ (e.g. $$ptr_obj = 0).

WWW: http://search.cpan.org/dist/XS-Object-Magic/