I signed up and took a look, and you are indeed correct. _Excorcism's_ lesson plan is broken. Raku is not. I have no idea why they are doing things the way they are, but what they have is not setup correctly. It's a shame. That might have been a decent teaching environment.

I have found better luck using repl.it to test code, and working through the Raku Course at https://course.raku.org/

Hope that helps