Thanks again toolic and grandfather. Now that I know what to call it, I see only 28 PerlMonks nodes in more than 10 years that discuss them.

The docs toolic point to say typeglobs "used to be the preferred way to pass arrays and hashes by reference into a function, but now that we have real references, this is seldom needed".

Done and done.

Ovid explains typeglobs well here: Re: Confused about typeglobs and references.