In case you want to go even deeper, you can note that previously, if you did this:
- Started
iex -S mix - Changed a file
- Called
mix compile - Called
recompile()in IEx
recompile() would not pick up the new module at all, because it had already been compiled. Elixir v1.18 makes it so recompile() works consistently AND adds the auto_reload option. Overall, it is all about playing better with multiple OS processes. 
