I did some research and was hoping to poke my head in here and point out a more elegant solution that used some magic to pull group 4 and everything after it, but alas, that's not possible with re (and I think only kludge-able with the PyPI regex module, which would also add another dependency).

This will probably do just fine. At some future point it might be nice for trigger to have an args property that tokenizes everything after the command (think argparse for Sopel commands), but that's a long way off if it even happens at all.