[Exim] Routers as Conditionals

Hi

I am listening to this list since some time and I have also read most of the
documentation.
Anyway, I am still not sure, how to implement things best. The
documentations seams to give a lot of possibilities, but no "best practice".

Here is, what I want to accomplish:

1. Use a router like a if-statement: If a condition is true, continue at
router a, else continue at router b.
2. Read information from a file into some place ($address_data, I think
would go). That information would be a somehow separated list including 0/1
boolean flags as well as the maildir folder, group and user id and some more
things.
3. I need to get hands on that parts inside my conditions.

I think it will be best to get these information first. I will use a lookup
against some table and if the adress does not match at all, it will fail.

4. How to drop a mail using a router.

I do not require complete solutions, I am only hoping for some directions
and hints. [Anyway, solutions to discuss are obviously also welcome.]

Thanks,
Steffen