[Exim] Making a router PASS

I'm just trying to get Exim4 running on my Debian system, and I can't figure out
how I can get a router to PASS.

It seems to me that it always either defers, accepts or fails - but pass just
isn't an option.

I'd like to be able to set $address_data in a number of routers, use
PASS_ROUTER=next, PASS, and have

next:
driver = accept
transport = local_delivery
require_files = /var/mail/$local_part/$address_data

and thus have 'next' accept or fail based on the file check. I keep rereading
the manual, and it seems that if a router passes, $address_data should be
available to the next router. otoh, if it fails it definitely isn't, and if it
accepts then no other router gets hold of it, so what do you have to do to
return 'pass'? And why does the manual talk about return values when there's no
syntax to return anything?
--
Derek