It's a small language that looks familiar if you know other imperative Algol-derived languages. The point is not in that, the point is a single binary for everything, and portability.

It's like busybox, which is unremarkable as Unix userland, but is interesting because it's a single small binary.

But beyond the standard Algolish stuff, XS seems to have quite a few modern niceties, such as traits, generics, closures, OOP, pattern-matching, and even algebraic effects.