I cannot take credit for it. The implementation is trivial and given

my late arrival to zsh I'm sure there are many implementations that do
the same thing already, likely even by the same name. That said, even
they didn't invent anything of importance: it really is a trivial
thing.

Trivial unless you need it, don't have it, and don't know where to get it.  I consider it fundamental on principle.

Roman.