I wasn't at all surprised at the many comparisons to Inside-Out Objects that popped up in this thread. They both see basically the same thing wrong with Perl's object system as it is normally used and try to fix it in different ways. I must admit that the closure method didn't do some things as well as I thought it would when the idea first popped into my head a few days ago.

With Inside-Out Objects, everything starts to look like a hash. With Closure Objects, everything starts to look like a subroutine. A subroutine call is ultimately more flexible than a hash lookup (unless you want to open the can-of-worms that is a tied interface). However, you have to put more work into it.

IMHO, Inside-Out Objects rely on subtle behavior on Perl's part that make some people feel uneasy. Further, the technique isn't necessarily easy to grasp, even to those that have already mastered Perl's regular object system. Closures aren't necessarily easy, but I suspect they will be easier to think about than the Inside-Out technique. They may also appeal more to those with a functional programming background.

Yes, Closure Objects do impose that the heirarchracy all use the closure technique. I think it's a net gain for freedom, even over Inside-Out Objects. It will ultimately depend on what you're trying to accomplish, though I suspect either technique will solve your problem if you put enough effort into it. Further, which technique is easier for your project may not be clear from the start.