I was taught in school that `0.1` is rational. Afaik it isn't in any lisps. I think that's the point the GP was making.
That said, while making `0.1 + 0.2 - 0.3` come out as exactly zero, with a clean and principled way to avoid things going pathological when the denominator gets large, is nice, it's hardly one of Raku's "main contributions to the programming language design space that I probably haven't seen elsewhere?"! :)