use strict; use warnings; 

my $file_read='C:/WINDOWS/system32/drivers/etc/hosts'; 
my $ha=[]; 
my $names={}; 
my $ips={}; 
#open (my $hf,'<',$file_read) or die "Can't open $file_read: $!";; 
my $hf=\*DATA; 
while (my $line=<$hf>) {
  chomp $line; 
#  print $line."\n"; 
  my $h={}; 
  $h->{line}=$line; 

  my ($pre,$comment)=split('#',$line,2); 
  $h->{comment}=$comment if ($comment); 

  if ($pre) {
      my @parts=split(/\s+/,$pre); 
      if (scalar(@parts)>1) { 
          my $ip=shift @parts;
          $h->{ip}=$ip;
          push @{$ips->{$ip}},@parts; 
          $h->{names}=[@parts];
          for my $name (@parts) {$names->{$name}=$ip; }
          } # parts 
      } # pre 
  push @$ha,$h; 
  } #line 
use Data::Dumper; 
print Dumper($ha); 
print Dumper($ips); 
print Dumper($names); 

#open($out, '>', $file_write)|| die "\n error opening file $file_write \n";

my $out=\*STDOUT; 
print $out "#Hosts file\n";
print $out "#Last Modified  -> ". localtime() . "\n";
print $out "# \n";
print $out "# localhost: Needs to stay like this to work\n";
print $out "127.0.0.1\t localhost\n";
print $out "# \n";
delete $names->{localhost} if ($names->{localhost}); 
my @ksort=sort {my $r1=$names->{$a} cmp $names->{$b}; return $r1 if($r1); $a cmp $b} keys(%$names); 
for  my $name (@ksort) {
  print $out $names->{$name}."\t".$name."\n";
  }
__DATA__ 
# Copyright (c) 1993-1999 Microsoft Corp.
#
# This is a sample HOSTS file used by Microsoft TCP/IP for Windows.
#
# This file contains the mappings of IP addresses to host names. Each
# entry should be kept on an individual line. The IP address should
# be placed in the first column followed by the corresponding host name.
# The IP address and the host name should be separated by at least one
# space.
#
# Additionally, comments (such as these) may be inserted on individual
# lines or following the machine name denoted by a '#' symbol.
#
# For example:
#
#      102.54.94.97     rhino.acme.com          # source server
#       38.25.63.10     x.acme.com              # x client host

127.0.0.1       localhost ads.pointroll.com scanner2.malware-scan.com localhost adsys.townnews.com adimages.townnews.com ad.doubleclick.net pagead2.googlesyndication.com ad.yieldmanager.com view.atdmt.com ads.revsci.net servedby.advertising.com jeffcity30.autochooser.com performanceoptimizer.com cache.fimservecdn.com pixel.quantserve.com ads.yimg.com this.content.served.by.adshuffle.com img-cdn.mediaplex.com cache.fimservecdn.com adserving.cpxinteractive.com pixel.quantserve.com s0.2mdn.net
127.0.0.1       www.zip2save.com d1.openx.org c3.openx.org partner.googleadservices.com media.ljworld.com everythingmidmo.com www.everythingmidmo.com edge.quantserve.com pixel.quantserve.com ad-g.doubleclick.net ads.yimg.com ad.wsod.com s0.2mdn.net s0.2mdn.net

192.168.1.1 nat.mylan 
192.168.1.100 dhcp1.nat.mylan 

192.168.2.1 wifi.mylan 
192.168.2.100 dhcp1.wifi.mylan 

192.168.1.234 lxle0 lxle0.mylan 
192.168.1.200 me me.mylan 
192.168.1.200 me me.mylan 
192.168.254.251 wan.mylan