Yes, I believe an implementation of Alter in terms of an inside-out class would be possible. From my perspective that would be a rather roundabout way. You'd require one call to ident()plus a hash acces to retrieve the alter ego.

More importantly, my goal is not to have to support garbage collection and thread cloning in the first place, but let Perl do it. These problems can be solved, and have been. I've done it myself in my module Hash::Util::FieldHash. I think it's far better not to have them in the first place.

I would like a pure Perl implementation, and I'm trying to keep the necessary XS part to a minimum, but I don't see one. Magic has the unique combination of being out of band to Perl code, but being serviced by garbage collection and thread cloning. Magic needs an XS part.

Anno

Update: I forgot to mention: No there isn't a set of tests yet with Alter.pm. It is entirely preliminary.