title: Does Parallel::ForkManager() module support synchronization on global variables?
body: <p>I'm very new to this <a href="http://search.cpan.org/perldoc/Parallel::ForkManager" rel="nofollow noreferrer">Parallel::ForkManager</a> module in Perl and it has a lot of credits, so I think it supports what I need and I just haven't figured out yet. </p>
  
  <p>What I need to do is in each child process, it writes some updates into a global hash map, according to the key value computed in each child process. 
  However, when I proceed to claim a hash map outside the for loop and expect the hash map is updated after the loop, it turns out that the hash map stays empty. 
  This means although the update inside the loop succeeds (by printing out the value), outside the loop it is not. </p>
  
  <p>Does anybody know how to write such a piece of code that does what I want?</p>