Haskell is the only language I ever learned (out of dozens, including Lisp and Forth) that felt like learning something completely new, like none of my existing

Haskell is the only language I ever learned (out of dozens, including Lisp and Forth) that felt like learning something completely new, like none of my existing programming knowledge applied. Working in Haskell means exploring a very different neighborhood in design-space. It's much more of a change of pace than learning about a specific layer of the stack.