Best way to get something like a register_before_redirect()

I am poking around in Phoenix and I have noticed the Phoenix conn structure is losing the raw post data after calls to redirect. I am interested in viewing the raw values submitted to the server. I can add IO.puts(inspect(conn)) in the controller portion of the pipeline before the redirect but I would need to do for every controller action that results in a redirect. I found the register_before_send options that works really well but it occurs after controller redirects.

Is there something I could do to similar to register_before_send to examine the initial post data before the redirect occurs?