I couldn't figure out the best place in the reply tree to post this, so replying to the OP, answering the questions, taking into account other discussion that has happened.
1) If this feature existed in Python 3.11 exactly as described, would you use it?
Definitely
2) Independently: Is the syntactic distinction between "=" and "=>" a cognitive burden?
No, but I feel there is some cognitive burden with the distinction between that and other arrow notations that we have now and will likely have later. 4) If "no" to question 1, is there some other spelling or other small change that WOULD mean you would use it? (Some examples in the PEP.) Technically this is not applicable since I would use it anyway, but… I would slightly prefer any one of the alternative syntaxes. At first, I was not liking the '@' prefix idea because the '@' is separated from the default expression that it is conceptually associated with. That option does have a strong redeeming aspect though, which is that I think it might be the easiest to read. 5) Do you know how to compile CPython from source, and would you be willing to try this out? Please? :) Sure. I don't think I need to try it to know that I would appreciate it though, unless I were to find that it is buggy or something.