[Exim] how do i use embedded perl

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I want to use embedded in perl in my exim configure file.
I compiled the binary with support for it but how do I use it?

I have this router

user_tes:
    driver = redirect
    domains = dbm;rewrite.db

The domains will be *.domain.co.uk for eg and i want to rewrite
test@??? to user@??? but i want to do it generically
for domains which exist in rewrite.db

I have a reg expression which will do it but need to know how to tie this
into the router . I know this is wrong syntax for exim but the perl is

$domain = "user.domain.co.uk" <- this would be passed as the domains
variable in exim?
$domain = =~ m/(.+?\.(+)/;

print $1@$2; <- would give me user@???

but i need the data variable in exim to be $1@$2

Anyone help please please

Dave
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