I’ll take a crack at that. To get the rate for USD, for example, you’d do something like:
var foo=plugins.http.getPageData('http://www.ecb.int/stats/eurofxref/eurofxref-daily.xml');
var bar=foo.match(/\n\W+<Cube currency=\'USD\'\W+rate=\'([0-9\.]+)\'\/>\n/);
application.output(bar[1]);
and likewise for other currencies. The tricky bit is the regular expression in line 2. It will be well worth your time to learn RegEx syntax thoroughly; there are lots of good tutorials on the web, perhaps someone has a favorite.