Does anyone know how to force certain-files/project to recompile if compiletime envvars changed?

Example I have a config.exs like so

region = System.get_env("REGION", "us") |> String.to_atom()
config :app, :region, region

and code that uses it

defmodule MyModule do
    if Application.compile_env!(:app, :region) == :us do
      def lol() do "United" end
    else
      def lol() do "United in another language" end
    end
end

I would like MyModule to recompile (outside a release setting) if REGION envvar changed.

Example doing

REGION=us iex -S mix
compile
REGION=us iex -S mix
nothing
REGION=ca iex -S mix
compile
REGION=us iex -S mix
compile

I can change compile_env to get_env, then the app just runs without recompiling anything. I rather not crash, and not false negative.