I've been doing Firefox extension development and it's been going pretty slowly because it's hard for me to figure out what's going on when things are running (and I'm not wildly familiar with the things I'm working with).
On an interesting note, you connect to MozRepl with telnet and it has a line-mode interface. Turns out that Lyntin (a mud client I worked on years ago) works fantastically for this. I would assume most mud clients would because at heart they're line-mode telnet clients with a bunch of features designed to remove repetition in common tasks and make it easier to skim large amounts of output quickly without having to read through all of it.
For example, say I was interested in skimming changes for the
title attribute. I could do this:
That will highlight lines with "title" in them from "title" onwards.