This command occurred to me today as a useful way to leverage the
thing-at-point machinery.

I've put together the attached implementation as a first pass, based on
what I could glean of the current thing-at-point functionality.

I didn't see any existing ways of listing known/valid things.  If I'm
gathering this correctly, it might be useful to separate that bit out
into another function.

What do you think?


-Phil