[Exim] Filters.conf question

This is a multi-part message in MIME format.
--
[ Picked text/plain from multipart/alternative ]
I am having trouble figuring out how many escapes are needed to
make my "Band-Aid and bubblegum on the dam" filter work.
I am trying to match the ".' and the country code.
I am also trying to match the end of the string, but
when I add the (regex) "$" I have to escape it with so many backslashes!
Looking for the hot tip.
Thanks,

     if "$sender_address:" matches "(\.tw|\.ru|\.pt|\.cn)"
     then
        logwrite "\n$tod_log  NOT_GOOD  $message_id  Host=
$sender_fullhost\n\t\
        \From=$sender_address  To=$recipients \n\t\
        \subject=$header_subject"
        #seen finish
     endif

Kurt White
Surf1 Communications
--