Thank you for your clear and complete reply. It illuminates questions I hadn't even realized existed until the advent of this thread.

... I think [the current solution] is the wrong solution because it creates a dichotomy.

It also seems likely to create a few face-plants when people stumble over this little oddity.

If you assign to a non-existent element of an array through a reference, a scalar is autovivified in that place ... And, IMO, a similar thing should happen when non-existent elements of an array are aliased by passing them to a subroutine.

This is certainly the behavior I was expecting, and that I would consider most useful.

Once again, thanks for this enlightening post.