%hash :shared = &share( {} );

##</code><code>##

lock %hash;
$hash{ existingkey } = newvalue;
# or
$hash{ newkey } = newvalue;
#or 
delete $hash{ existingkey };

##</code><code>##

lock %{ $hash{ foo } };
$hash{foo}{somekey} = somevalue;
# or
delete $hash{ foo }{ somekey };