It's quite ok to overwrite buildin functions, but it's awfully bad that we cannot even debug our solutions. This kata is obviuosly bad style kata.

I would have to add, having a challenge (Kata) that introduces a user to overwrite builtin functions is bad practice without context. Took me a minute to catch on, but this one should have been vetted or at least provided some context as why one would have to re-construct builtin functions.