#! /usr/bin/env perl

use strict;
use warnings;
use Getopt::Long;
use POSIX ":sys_wait_h";

GetOptions('-i=s' => \my $infile);
       
my ($counter,$index,@lines) = (1,0);

open my $fh,"<",$infile or die "Can't open $infile: $!";
while(my $line = <$fh>){
  push @{$lines[$index]},$line;
  $index++ if $counter++ % 10 == 0;
}

fork_it(\@lines);


#------------------------------------------#
# Subroutines                              #
#------------------------------------------#



sub do_something_with_lines{
  my ($lines,$nr) = @_;
  print $nr,": ",$_ for @$lines;
}


sub fork_it{
  my ($linesref) = @_;
  
  my %pids;
  
  for (1..scalar(@$linesref)){
    my $pid=fork();
    if($pid==-1){
      warn($!);
      last;
    }
    if($pid){
      $pids{$pid}=1;
    }
    else{
      do_something_with_lines($linesref->[$_-1],$_-1);
      exit(0);
    }
  }
  while(keys %pids){
    my $pid=waitpid( -1, WNOHANG );
    die "$!" if $pid == -1;
    delete $pids{$pid};
  }
}