[exim] Copy/duplicate a mail depending of the sender address

Hi,

i need to duplicate specific mails in exim depending on the sender address.

I have this working for now:

copyrouter:
        driver = redirect
        senders = localpart1@???
        data = localpart1@???
        unseen
        no_verify

So for more senders i could use more routers like this, but maybe a lookup
to a textfile would scale better.

I thought about a file (eg. /etc/exim4/copylist) with pairs of

localpart1@???: localpart1@???
localpart2@???: localpart2@???

and so on, but i could not figure out how to lookup and use these entries
in a router.

Can someone help me with an example how to do that?

Greetings,

Matthias