Forcing Nginx to render response from Rails application

Hi, I’m using Nginx with Phusion Passenger, and I would like to render
some responses from Rails App even though file exists at that URI on
server. I want to do this based on subdomain from which request is
coming. Is something like that even possible? I’ve managed to do
redirect based on this conditions but it would be better if I could do
that internally, without change to URL.

Posted at Nginx Forum:
http://forum.nginx.org/read.php?2,77960,77960#msg-77960