use strict;
use feature ':5.10';
use Parallel::ForkManager;

our $pm = Parallel::ForkManager->new(8);

$pm -> run_on_finish ( # called BEFORE the first call to start()
    sub {
        my ($pid, $exit_code, $ident, $exit_signal, $core_dump, $data_structure_reference) = @_;

        # retrieve data structure from child
        if (defined($data_structure_reference)) {  # children are not forced to send anything
             my $string = ${$data_structure_reference};  # child passed a string reference
             if ($string) { 
                  #how to process $string? 
             };
        }
        else {  # problems occurring during storage or retrieval will throw a warning
            say qq|No message received from child process $pid!|;
        }
    }
);

LOOP:
foreach my $instance (0..100) {
    $pm->start and next LOOP; # do the fork
    my $data;
    foreach my $i (0..50) {
        push(@$data,int(rand(10));
    }
    $pm->finish(0,\$data); # exit the child process
}

$pm->wait_all_children;