reverse proxy with relayd(8) (but not nginx)

Hi,

I'd like to setup a http reverse proxy where http://foo.org/someapp is
forwarded to 127.0.0.1:8081 and http://foo.org/* is forwarded to
somewhere else.

AFAIU, it is not possible with httpd(8) so I'm trying to do this with
relayd(8). There is an example in httpfiler protocol in
/etc/examples/relayd.conf that does this to block an url:

# Block disallowed sites
match request label "URL filtered!"
block request quick url "www.example.com/" value "*"

But, I can't make it to forward to a server and port. Does anyone have
such a config?
--
Manuel Giraud