Janet has the pieces for this in the spork stdlib with netrepl combined with fibers, but there's no standard or pre-configured way to set it up. Its current app

Janet has the pieces for this in the spork stdlib with netrepl combined with fibers, but there's no standard or pre-configured way to set it up. Its current approach to namespaces doesn't particularly allow for it either, so you have to choose one of a few various hacks for redefining things as you noticed. People have been asking for it and demonstrating proofs of concepts for the last year or so so it wouldn't surprise me to see it formally addressed soon. But I don't know, I don't have any particularly insight I just like that language and keep half an eye on it.