I'd put the question this way: assuming Matcher can be written (with a bit of stack magic), and assuming that the strings inside m.case() calls are exactly the same mini-languague PEP 634 proposes, would you want a syntax change?

No, I wouldn't!

Is one of us mixing up negations? Are you saying you do NOT support PEP 634 (i.e. syntax change)?

A reasonable enough opinion that several core developers hold. Just trying to understand.

Sorry I wasn't clear. I wouldn't want a syntax change specific to matching if it could be done with a library. I just don't think it can be done with a library without other language changes. But I think those other language changes could be used in ways outside of just matching.

Eric