my %hash = (test => 1);
my %otherhash;

  use Parallel::ForkManager;
  my $pm =  new Parallel::ForkManager(5);
	for(1..10000){
		my $pid = $pm->start() and next;

		# some operations involving waiting etc.

		if(exists($hash{test}){
			# this exist test always fails!
		}

		# write some data to otherhash
		$otherhash{test} = 123;

		$pm->finish();
	}

	# the data 123 never arrives here...:
	print $otherhash{test};

...