Huh, if the local various was only scoped to the closure block, and not above it, I would never expect it to be shared. I would think "avoid using closure state" means exactly that, use only local variables scoped no higher than the closure block itself. (It's true this can sometimes be difficult to ensure in ruby; block local variables can help).

Do I understand things right, or am I wrong here?

I guess the question is where the regexp special vars are scoped to though, I see how that's not entirely clear.