I'd go with something like this...
function checkValidDomains(host) {
var validDomains = ['x.example.com', 'y.example.com'];
if (!(validDomains.indexOf(host) > -1)) {
s.abort = true;
}
}
s.doPlugins = function (s) {
checkValidDomains(document.location.hostname);
};
If you don't already have doPlugins set up in Launch (or your AppMeasurement.js library), it's easy to do, and if someone happens to copy and use your analytics script verbatim, you'd be covered on ALL analytics calls. No need for rule-specific conditions or anything more complicated.