It allows users to further customize IEx.
For example, it could be useful to include additional
information in the prompt:
Erlang/OTP X [erts-x.x] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [hipe]
Interactive Elixir (1.x.x) - press Ctrl+C to exit (type h() ENTER for help)
production - read-only session - i-abc435123asd12323 - eu-west-1
iex(1)> if true do
...(1)> :ok
...(1)> end
:ok
production - read-only session - i-abc435123asd12323 - eu-west-1
iex(2)>