use Perl

Here are two, vaguely unrelated, questions that I am earnestly and eagerly searching for answers for:

• In Firebird Mozilla, how would I go about writing a bit of JavaScript (to be put in my user.js file) that would, every time I load an HTML page, set an attribute "_domain" on the root node of the DOM tree; the domain value would just be the hostname from the page's URL. I want this so I can write my own little stylesheet do-dads (in my chrome/userContent.css) that would target some sites that I commonly visit and that I really want to alter my personal view of -- notably making them a bit easier on my poor-excuse-for-eyes by forcing a particular text size and text colors, etc etc. (I know there's features for forcing ALL text on ALL web sites to be a particular size and color, but that's disastrous in most cases.)
• I'd really like to learn how to write Firebird extensions -- I have some decent i18n/interface ideas I'd like to try out, and I think people would find them useful. But I simply can't find a page that describes the process of writing and binding a bunch of JS functions, and making a dist out of them.

I would simply ask a Firebird developer these things, but I don't know any who aren't so maddeningly overworked at smashing bugs that they could ever answer email from a random unknown person asking for help. Does anyone here know anyone who could lend me a hand and answer my occasional questions about these sorts of things? I've written a bit of Perl software in my day, and I expect that I can pull off some interesting stuff in Firebird.