http://www.perlmonks.org?node_id=567058


in reply to Re: Autovivification trick
in thread Autovivification trick

there should be a module designed for exactly this kind of things
The only thing I found (during my admittedly limited search) was Data::Hierarchy - could that have been the one you were thinking of? It appears to be somewhat specialized and may not quite satisfy the same requirements that your snippet does, but it's the closest thing that I found.