arguments passed to a trigger function

In the create_trigger man page:

EXECUTE PROCEDURE func ( arguments )

But what kind of arguments can be passed? It is not explained in the
documentation.

After looking at regress.c I undestand that these arguments are
contained in TriggerData->tg_trigger->tgargs but I can't seem to pass
anything useful to the procedure beyond random text strings at the
"CREATE TRIGGER ... " stage.

Thanks in advance for your insight,

--
Louis-David Mitterrand - ldm(at)apartia(dot)org - http://www.apartia.fr