[exim] Clarification on detainting in exim 4.94 router

[Adam via Exim-users]

Hello,

I have the following router and transport for delivery to a ticketing 
system. There's an issue here with $local_part. Isn't it detainted by 
the use of local_parts to only run this if $local_part was found in the 
file? I'd appreciate some advice on the correct way to do this in exim 
4.94. $local_part_data is blank.

# router
request_tracker:
  driver            = redirect
  domains           = rt.example.com
  local_parts       = /usr/local/etc/exim/queuenames/list.of.requestors
  local_part_suffix = -comment
  local_part_suffix_optional
  pipe_transport    = request_tracker_pipe
  data              =   "|/usr/local/bin/rt-mailgate \
                        --queue \"${local_part}\" \
                        --action ${substr_1:${if 
eq{$local_part_suffix}{} \
                        {-correspond}{$local_part_suffix}} } \
                        --url http://rt.example.com";
  user              = mailnull

# transport
request_tracker_pipe:
  driver         = pipe
  return_fail_output
  allow_commands = /usr/local/bin/rt-mailgate

Thanks,
Adam

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