[anfelor]

These are two different languages, see https://effekt-lang.org/ and https://koka-lang.github.io/koka/doc/index.html -- although I believe that the FP^2 work mentioned by OP currently only works in Koka (and perhaps soon in Lean; https://leanprover.github.io/)

[di4na]

Indeed.

That said i am slowly writing my own language that will probably use ideas from both :D