Hmm, I just tried that but it didn't work. The STORABLE_thaw() method gets called from Storable's XS code, which may explain the problem.

I think that Storable calls STORABLE_thaw with a blessed reference of the appropriate type (in my case a hash ref) and then looks directly at the _referenced_ data after calling the method, as opposed to looking at the reference itself.

So I need a way to switch the referent out from under the reference.