Hrm, I can see why we added this heredoc check but I think we should remove it because there are many cases where the indentation can be off on purpose besides heredocs, like:

    iex> foo
    [ some complex structure,
      more structure ]

I think what we need to do is something like:

1. Once we see the first `iex>`, we get its indentation;
2. All subsequent `iex>` must have the same indentation as above;
3. Every line right after the `iex>` line must have the same indentation as above;
4. All other lines are simply stripped by the number of indentations characters.

This should make heredoc work out of the box and support the other cases. What do you think?

Thanks a lot @thmzlt !