Currently, its possible to use the 'suppress' field and 't' options of the /Pb macro to capture text and pass to Perl. The 't' allows trace information to be sent to Perl as well.
However, when sending data back to XPP the trace information is ignored or has to be removed to avoid errors.
It should be possible for the XPP style developer to modify or remove the trace information (and/or the textual data) and send back to XPP for composition.