The shell is already a process. The magic words are spawn, and send. You might also want to learn about Link and Monitor, which are the basic blocks, on which OTP is built upon.
$ iex
Erlang/OTP 21 [erts-10.2.3] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe]
Interactive Elixir (1.8.1) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> self()
#PID<0.107.0>
iex(2)> calculate = fn a, b, _action -> IO.puts(a + b) end
#Function<18.128620087/3 in :erl_eval.expr/5>
iex(3)> spawn fn -> calculate.(1, 2, :add) end
3
#PID<0.111.0>
This example just print some output, but You can pass self() as a parameter to the message, and have the spawned process send back the result to the calling process.
iex(1)> pid = self()
#PID<0.107.0>
iex(2)> calculate = fn a, b, pid -> send(pid, {:result, a + b}) end
#Function<18.128620087/3 in :erl_eval.expr/5>
iex(3)> spawn fn -> calculate.(1, 2, pid) end
#PID<0.111.0>
iex(4)> flush
{:result, 3}
:ok
You might like
https://www.cs.kent.ac.uk/ErlangMasterClasses/
in particular Master class 2, which is about turning sequential programming into concurrent.
