_output

$ ls
other_thing.exs
thing.exs

$ elixir thing.exs                                                                                                                    
calling other
other thing!
hooray!

other_thing.exs

defmodule OtherThing do
  def other do
    IO.puts "other thing!"
  end
end

thing.exs

defmodule Thing do
  Code.require_file "other_thing.exs", __DIR__

  def do_something do
    IO.puts "calling other"
    OtherThing.other()
    IO.puts "hooray!"
  end
end

Thing.do_something()