Three Monkeys, Three Typewriters, Two Days

Indeed-o!

Actually, I think you can do it nicer, and maybe even perfier, but you need to switch js1.7 on:

function enumURLPairs(list) {
for each (var tuple in list) {
do_check_eq(tuple.length, 2);
yield tuple.map(stringToURL);
}
}

for each (var [provided, target] in enumURLPairs(paris) {
// do foo
}

This way you don't create the intermediate array.

PS: Sorry, I don't think I can indent.