[exim] Conditional header rewriting

Greetings,

The task is simple: i need to rewrite header addresses if and only if
certain condition is met. E.g.

If
To/Cc/Bcc contains @domain.example.com
Then
<address rewrite rule>

Can it be done *without* calling external program? May I ask for a
snippet of exim.conf code, if yes?

Thank you.