Erlang is magic!

magic.erl

-module(magic).
-export([loop/0, start/0]).

loop() ->
  receive
    Fun ->
      Fun(),
      loop()
  end.

greet() ->
  io:format("Hello, world!~n").

start() ->
  To = spawn(magic, loop, []),
  To ! fun greet/0,
  To ! fun() -> io:format("Erlang is magic!~n") end,
  ok.

% $ erl
% Erlang/OTP 22 [erts-10.4.3] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe] [dtrace]
% Eshell V10.4.3  (abort with ^G)
% 1> c("magic.erl").
% {ok,magic}
% 2> magic:start().
% Hello, world!
% ok
% Erlang is magic!
% 3>