[exim] Filtering e-mail by subject and redirecting to a pipe

Hi,

yes, I am a newbie to this and yes, I read the documentation and also
several articles about my "problem". It seems, I am too stupid or just
too far away from the right way to realize it :-)

Using Exim 4.x (at the moment: 4.50), I want to filter e-mails by some
special subjects and pipe them into an external (Perl-)program. What
I got so far:

 * a redirect router allowing filtering
 * a filter file performing something like:
   if $h_subject: contains "blahblahblah" then
       pipe /path/to/script
   endif

To be more concrete...

... /etc/exim4/exim4.conf:

| begin routers
|

| test_subject_router:
|         driver = redirect
|         allow_filter
|         file = /etc/exim4/filtersubject
|         user = mail

... /etc/exim4/filtersubject:

| # Exim filter
| if error_message then
|         finish
| endif
| if $h_subject: contains "blahblahblah" then
|         pipe /path/to/script
| endif

When an e-mail arrives, nothing more happens than "normal" and local
delivery.

Do I have to define a "local_part" within the router configuration?

Any hint would help. Thanks in advance! :-)

    Thomas
-- 
 ..:: Thomas Gericke :: "Live every day as if it were your last" ::..
   :: <mailto:thomas@thomasgericke.de>
   :: <http://www.thomasgericke.de/>
-- 
 "So, I poured another strong one 
  And chopped a line from here to Texas 
  Cause I've lost another good one 
  She's on the midnight train to Memphis"