The underlying language isn't really very mathematical, at most there's a bit of linear algebra in the primitives but that's it. You certainly don't need any sort of formal maths education to learn APL. There are about 50 or so new symbols, which is not a big ask, with any sort of focus the majority of the syntax etc can be learned very quickly. The "bugs" in your original code stand out very clearly because things like "∘}" don't make sense, ∘ being "dyadic" (infix).