event_after_every/2

Hi,

I want to do some simple event handling and the
event_after_every/2 predicate seems to be exactly what I need.
Unfortunately, when I run the sample program:

setup :-
 set_event_handler(call_hi, hi/0),
 % set up event `hi' to occur every 3.2 seconds
 % and the hi event will trigger the execution of hi/0.
 event_after_every(call_hi, 3.2).

hi :-
 writeln(hi).

it just succeeds without any printouts.
Anyone who has experience with that?

Thanks.

Andreas