Should I use GHC Haskell extensions or not?

Question

As I am learning Haskell, I see that there is a lot of language extensions used in real life code. As a beginner, should I learn to use them, or should I avoid them at all cost?

Answer 1

Yes, use extensions as appropriate.

But be sure to enable them intentionally -- only when you decide you need them. Do this on a per-module basis via {-# LANGUAGE Rank2Types #-} (for example).