程序的格式如下：

 1:  use Parallel::ForkManager;
 2:  
 3:  $pm = Parallel::ForkManager->new($MAX_processes)
 4:  # 设置最大的线程数目
 5:  
 6:  foreach $data (@all_data)
 7:  {
 8:      # Forks and returns the pid for the child h
 9:      my $pid = $pm->start and next;
10:      ... do some work with $data in the child process
11:      $pm->finish; #终止子进程
12:  }

如果没有这个模块的就剩下如下的内容：

1:  foreach $data (@all_data)
2:  {
3:      ...do some work with $data in the child process
4:  }
5:  #也就是上面比这里多了四行，非常容易使用