lock on hashtable value

hi all...
i have a question..

I am realizing an application multithreaded, and my problem is that I'd like to make lock on single values of a hashtable.. how can i make it? my hash is shared with

share($hash);
$hash = \%hash;

but all elements of this are not shared.. so how can i share all them ?

i have seen this http://perldoc.perl.org/threads/shared.html but i haven't resolved...

anyone can help me? thanks

bye Valerio

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