spawn.ex

defmodule Greeter do
  def greet do
    receive do
      {sender, msg} -> 
        send sender, {:ok, "Hello #{msg}"}
        greet
    end
  end
end

pid = spawn(Greeter, :greet, [])
send pid, {self, "world"}
receive do
  {:ok, msg} -> IO.puts msg
end

# Hello world

send pid, {self, "kermit"}
receive do
  {:ok, msg} -> IO.puts msg
end

# Hello kermit