perlbal and a server not supporting some operations NOT_SUPPORTED

I have 10 server running my website.

I reimplemented 90% of the server and I need to test it in one server. So my mod_perl script has to say that it isn't able to provide 10% of the requests and send it to any other server.

Someone told me that I should look to the NOT_SUPPORTED, but I found nothing.

So how can I implement this? The perlball has to understand that exist a problem in this request, and send it to another server.

Thanks for the help