first:rev is already resistant to changes in first or rev
Oh, good to know. ^_^ For Penknife, I tried to make [= foo a:b] produce a custom syntax if a or b was a custom syntax, but I got stuck. I ended up with [foo ...] using the local values of a and b, I think. In the process I got a bit confused about how a:b was supposed to work in the edge cases, from a design point of view.
This experiment was reflected in two commits in the Git repo: One introducing it, and one removing it 'cause of the poorly thought-out complexity it introduced. :)
Here it is. https://github.com/rocketnia/penknife/commit/3ca7a6c216cc022... Penknife's significantly more complicated than what I've been able to talk about so far, with its own ad hoc vocabulary throughout, so good luck. ^^; Then again, that's a pretty old commit, so it's actually a simpler codebase in ways. XD
