RE: [Exim] Routers and prefix?

>Exim 4.21 (bad luck!) has a new option called rcpt_include_affixes as a
>generic transport option; it puts the affixes back at transport time.
>
>Otherwise, you have to do it without making use of local_part_prefix.
It
>can usually be done, but more clumsily.

I spoke to soon, I seem to be running out of time to upgrade
exim/exiscan. Can someone shed light on how I could do this without
using prefixes?