[exim] :defer: in redirect router?

Hello Exim Experts,

I must be misinterpreting this, from the spec:

---

During routing for message delivery (as opposed to
verification), a redirection containing :fail: causes
an immediate failure of the incoming address, whereas
:defer: causes the message to remain on the queue so
that a subsequent delivery attempt can happen at a
later time. If an address is deferred for too long, it
will ultimately fail, because the normal retry rules
still apply.

---

I have this router:

inbound_doorman_exim_errors:
   driver = redirect
   domains = maildance.com
   local_parts = doorman
   condition = ${if and { {! def:sender_address}\
                          { eq {$received_protocol}{local}}\
                    }{yes}{no}}
   data = :${if eq {${readsocket {SOCKET_NAME}{doorman_errors.py exim \
                          X-Failed:  ${quote:$h_X-Failed-Recipients:} \
                         X-Delayed: ${quote:$h_X-Delayed-Recipients:} \
                      $message_body}{3s}{problem}}\
                    }{OK}{blackhole}{defer}}:

But I get this:

2005-01-20 11:01:55 1CrhZ5-0003W8-HS == doorman@???
R=inbound_doorman_exim_errors defer (-17): error in redirect data:
":defer:" is not permitted

If the socket sends back 'OK', it is taking responsibility for the
message and so I want it dropped in a :blackhole:, if there's a
problem, I want it to :defer:

Any help would be greatly appreciated, as always.

Marilyn Davis