How do you get the response from the Request object in MooTools?

Question

How do you access the response from the Request object in MooTools? I've been looking at the documentation and the MooTorial, but I can't seem to make any headway. Other Ajax stuff I've done with MooTools I haven't had to manipulate the response at all, so I've just been able to inject it straight into the document, but now I need to make some changes to it first. I don't want to alert the response, I'd like to access it so I can make further changes to it. Any help would be greatly appreciated. Thanks.

Edit:

I'd like to be able to access the response after the request has already been made, preferably outside of the Request object. It's for an RSS reader, so I need to do some parsing and Request is just being used to get the feed from a server file. This function is a method in a class, which should return the response in a string, but it isn't returning anything but undefined:

        fetch: function(site){
                var feed;
                var req = new Request({
                        method: this.options.method,
                        url: this.options.rssFetchPath,
                        data: { 'url' : site },
            onRequest: function() {
                                if (this.options.targetId) { $
(this.options.targetId).setProperty('html',
this.options.onRequestMessage); }
                        }.bind(this),
                        onSuccess: function(responseText) {
                                feed = responseText;
                        }
                });
                req.send();
                return feed;
        }

Answer 1

Is this what you're looking for?

var req = new Request({
    method: 'get',
    url: ...,
    data: ...,
    onRequest: function() { alert('Request made. Please wait...'); },

    // the response is passed to the callback as the first parameter
    onComplete: function(response) { alert('Response: ' + response); }

}).send();

Answer 2

I was able to find my answer on the MooTools Group at Google.