Simply aliasing a participant.

    engine.register_participant "toto" do |workitem|
        workitem.toto_message = "toto was here"
    end
    engine.register_participant "user_.*", AliasParticipant.new("toto")

Workitems for participant whose name starts with ‘user_’ will be handled by participant ‘toto’. Note that you can‘t use use a regex as the aliased name ("toto" in the example).