Perl && jQuery && XML && ! taconite
If you're in a hurry, jump to my latest (6th) Perl + jQuery tutorial.
In short: I don't use the clever jQuery add-on taconite because it supports only commands (verbs) and I needed conditional execution (an 'if').
Nevertheless, I pinched-er-adapted the idea to unilaterally update some parts of the DOM, and to conditionally update other parts.