Long standing annoying issue in ghci

[MarLinn]

> Here's what I use:
>
> :set prompt "\ESC[46m\STX%s>\ESC[39;49m\STX "
>
> I believe \STX is a signal to haskeline for control sequences.
> Documentation is here:
> https://github.com/judah/haskeline/wiki/ControlSequencesInPrompt
Note: If you're using a multi-line prompt, things may be different 
again. I don't know what the rules are, but I found that if I put \STX 
on any but the last line of prompts I get weird characters. The same 
goes for any \SOH you might want to add for some reason.

Cheers,
MarLinn