If you check the errata #77244, that's his ONE SINGLE example of how you can use pattern matching with maps. I smiled as I read the example. But when I tried it, boom! That piece of code does not run on any released version of Erlang, and I am here trying out Erlang to see if I can use it in my enterprise project! The most disappointed I have been while learning any language.

    count_characters([H|T], #{ H := N }=X) -> …