IMHO, if HTML::Template were to allow such a wide open definition of what it accepts, it would be a support nightmare. Accepting every tied and overloaded data-structure would certainly degrade performance for plain old everyday hash-refs.
Personally, I think HTML::Template is fine as it is. It's very stable, extremly usable and has a simple and well defined API/interface. Subclass it if you want it to do these things.
I actually think your argument is more with tie than it is with HTML::Template. ( Overloading the %{} operator still requires you to return a hash-ref. If you dont want to return a real hash-ref, then it needs to be a tied hash-ref (see the overload doc for more info) ) What I think you really want is for tie to say "i am a hash" rather than "you can treat me like a hash". But to be honest, I am not a fan of that approach though.
-stvn
