(forks) When do I need to lock variables?

Hi.

I've playing around with forks and forks::shared for some time now - it
looks really nifty. In the past I've been spending too much time
emulating threads in Perl. :/

I am not quite sure when I need to lock. Is "$HASH{foo}++" safe? How
about "$foo = scalar keys %HASH"? Should a wrap access to shared lists
and hashed with tie and lock there?

-- 
There are only 10 different kinds of people in the world, 
those who understand binary, and those who don't.