Effect of 'drop/discard' in HTTP_RESPONSE event?

By default, HTTP::retry may just resend the original request, but you can supply a different one for it to send instead. However, if you cannot send any HTTP request at all to your second server (meaning, the server that is going to supply the response which causes a response to be sent to the client), then I don't see any way for you to accomplish this. In such a case, what are you sending to that server? I mean, you're not expecting that server to initiate the TCP connection, right?