My .iex.exs is exactly as you suggested.
When I run iex, I see this error message:
** (CompileError) .iex.exs:11: module MyHelpers is not loaded but was defined. This happens when you depend on a module in the same context it is defined. ... If the module is defined at the top-level and you are trying to use it at the top-level, such is not supported by Elixir
