Using dot-forward on exim4

I’ve been mentioning my plans to change my email routing on my wiki but there was one missing feature on exim. I’m currently using the so called dotforward stuff from courier. Actually, the forward rules I’m using are pretty simple. I have a .forward to send the mail to another email adres and I have a .forward-default to prevent mails with a dash send out. Searching for the same system on the internet didn’t gave me any satisfying solutions. But reading the manual of exim gave me a ratter easy solution: the use of exim filters. Especially the filter part was pretty useful. This is my result:
# Exim filter
logfile $home/filter.log
if $local_part_suffix is ""
then
deliver myotheremail@someprovider.com.spam
save Maildir/
else
save Maildir/.test/
finish
endif

So everything without a local part gets sended to myotherprovider, exactly the way I wanted.