use Parallel::ForkManager;

$pm = new Parallel::ForkManager($MAX_PROCESSES);

my @task_details = (
  # data needed for each sub-process
);

foreach my $task (@task_details) {
    $pm->start and next; # do the fork

    # do the sub process work using whatever details are in $task

    # write the results to a file somewhere, perhaps with a
    # pre-set name passed in $task

    $pm->finish; # do the exit in the child process
}
$pm->wait_all_children;

# Continue in parent and read in the results