[Exim] headers_rewrite

Hello to everybody,

I've got a problem.
I need to process address (To:) of incoming mail using headers_rewrite option,
e.g. I should change user@??? to user_domain_dom@???

  Here it is part of TRANSPORT CONFIGURATION section
        local_delivery_cyrus:
        driver = pipe
        headers_rewrite = *@* ${sg{$1_$2}{\\.}{_}}@$2 t
        command = "/usr/local/cyrus/bin/deliver -m ${local_part}"
        user = cyrus
        group = mail
        return_output
        log_output
        prefix =
        suffix = 
My cyrus should deliver message to user_domain_dom mailbox, but cyrus does't..
This headers_rewrite does't change e-mail address at all.

I tryed:
local_delivery_cyrus:
        driver = pipe
       command = "/usr/local/cyrus/bin/deliver -m ${sg{${local_part}_${domain}}{\\.}{_}}"
        user = cyrus
        group = mail
        return_output
        log_output
        prefix =
        suffix = 
But in vain .

Could anybody help me to solve it, or is there another possibility to fulfil it?
Any help would be appreciated

Thanks
__________________
Igor Vasiliev
igorvv@???