[Exim] ?Rewrite filter?

Please explain me how to create rewrite filter? 
I need:
#Special rewrite
    if
        $header_subject: contains "String0" or 
        $message_body contains "String1"
       then  

                $replay_address:  user@???
    endif 
#All 

       *@localdomain  *@isp.com FfRs
                                 ^^^^^^^^^^ this line working ok
but not special rewrite.