Most but some don't. This fails in Erlang

    X = X + 1.

because even variables are immutable.

This is ok in Elixir even if it kind of fakes it [1]

    x = x + 1

and it's perfectly ok in Ruby and most other languages.

[1] http://blog.plataformatec.com.br/2016/01/comparing-elixir-an...