UriPolicy questions

[J]

Hi all,

If I understand correctly, it is possible to set a UriPolicy so that
anything cajoled will have any URI requests rewritten? e.g., if a
script normally does an XmlHttpRequest to say, www.evil.com (for the
sake of continuing the examples), this script will be rewritten so
that all URIs now goto localhost, for example?

Is there an example of how this is done in practice? I'm new to Caja
and excited about its possibilities, but I didn't understand that
portion of the wiki very well.

(Link to wiki: http://code.google.com/p/google-caja/wiki/UriPolicy )

Thanks in advance!
-J