I assume you are using either version 0.68 or 0.69 of SOAP::Lite, it appears that in these versions the specific line that does the MIME packaging is commented out at line 1554 in Lite.pm:

   # Sometimes SOAP::Serializer is invoked statically when there is no
+ context.
  # So first check to see if a context exists.
  # TODO - a context needs to be initialized by a constructor?
  if ($self->context && $self->context->packager->parts) {
  # TODO - this needs to be called! Calling it though wraps the payloa
+d twice!
  #  return $self->context->packager->package($self->xmlize($encoded))
+;
  }
[download]

/J\