Python, for all its power and popularity, has long lacked a form of flow control found in other languages—a way to take a value and match it elegantly against one of a number of possible conditions.

I also just realized that I sort of sketched the basics of "algebraic matching", where the original PEP completely bypassed that issue and (x, x) doesn't even do what seems obvious? Or am I reading ...

Apparently the PEP authors decided to punt on what they call "algebraic matching" of repeated names. IMNSHO, if this PEP isn't doing algebraic matching then it's really far from clear what it's for, ...