Automatically adding proxy to all HTTP connections in ruby

I have an application that initiates multiple HTTP connections and I would like to add a proxy to all connections.

The application is using net/HTTP, TCP sockets and open-uri so ideally I would like to be able to patch all connections initiated from those libraries instead of adding it manually to each and every location in the code that initiates a connection.

Is there a way to accomplish that (on Ruby 1.9.2)?