Elixir is an application that runs on the Erlang VM. Libraries can be brought in and started as their own applications, with their own lifecycles. I'm not privy enough in the specifics of the Rust way of things, but it sounds like this is sort of similar if you squint a little bit?
Observer screenshot from a blank IEx session: https://puu.sh/xI3re/3701a0c64e.png