Re APL I totally know what you mean. I've never done anything with that category of language that wasn't just golfing / goofing around, but conceptually it's made an impression. Once the big picture concept clicks you look at the way we write most code and see so much bookkeeping that's just managing names and values of iterators and indexes. Lifting that up to bulk transformation of multidimensional objects is powerful, and much closer to the intuitive picture of what's going on I have in my imagination.