Fair enough. I guess I was hoping that since you advertise speed as an argument for Object::InsideOut you would be curious as to how Moose achieves such a big leap in performance through immutability and see if something similar could be done to OIO :)
I gave make_immutable a glance and it looks like a mix of subroutine memoization and inlining of accessors and constructors. I didn't go as far as trying to figure out what exactly gave it the performance boost for the benchmark though. I did however run NYTProf on Object::InsideOut during the benchmark and came away with the impression that OIO was probably paying a non negligible price doing hash lookups in %GBL and copying the string $class around in various places. The subroutine 'is_sharing' also got flagged by NYTProf as time intensive. (Note that if you're interested in running NYTProf yourself, you'll have to replace a few 'goto' statements in InsideOut.pm as that is a limitation of NYTProf).
You're right though, for my needs I can probably simply revert to something simpler for my short-lived classes.