[exim] Pipe transport in router data statement

Greetings

I have the following that works well (based on ECM exim + webinterface etc) :

mysql_aliases:
  driver = redirect
  allow_fail
  allow_defer
  data = ${lookup mysql{select smtp from users,domains \
                   where localpart='${quote_mysql:$local_part}' \
                   and domain='${quote_mysql:$domain}' \
                   and users.domain_id=domains.domain_id \
                   and users.type='alias'}}

However, a new requirement has reared it head where I need to be
able to redirect to a pipe "|/etc/exim4/eticket_support.pl" for a
proposed eTicket support ticketing system
(http://eticket.sourceforge.net/) and I found a possible solution on
on their forum (http://sourceforge.net/forum/message.php?msg_id=4208727)

From what I can surmise, I need to duplicate my working router and
added a statement in the "data" part to check for $local_part that
start with a pipe ( | ) and exclude it in teh first router and include
it in the second but I have no idea how to do that. Would it be
possible for a kind soul to post an example?

The rest I should be able to sort out myself once I have the correct
"data" lookups

Regards
Michael