I think you've hit the nail on the head there.

Contorted control flow can sometimes be handy, but as it can lead to a maintenance nightmare it deserves a warning.

Perhaps more importantly, there's probably some history to why last works that way in Perl, too. Raising the warning and providing the former functionality rather than breaking the functionality is a good compromise for features that have been declared as questionable practice.

Update: s/questionably/questionable/; to clarify that last sentence a bit.