[Exim] running filters from pipe redirects

HELO,

I'd like to have a possibility to use a filter file (.forward-like)
when running from /etc/aliases. The entries in aliases aren't real user
accounts, and they don't have a home directory where I could put .forward.

With procmail one could use '-m' command line switch to specify
the config file. How can I do the same with Exim filtering mechanism?

Marcin