Shell Programming and Scripting

use strict;
use warnings;
use MIME::Lite;
my (%ip, %host, $duplicate_ip, $duplicate_host);
my $host_file = '/etc/hosts';
open my $file, '<', $host_file or die "can't open $host_file $!";
while (<$file>) {
   if( my ($ip, $host) = /^#?([\d.]+)\s+(\S+)/ ) {
       s/\s+\b/\t/g; 
      push @{$ip{$ip}}, $_;
      push @{$host{$host}}, $_;
   }
}
close $file;
#print "Duplicate IP's with hostnames\n";
foreach my $ip ( keys %ip ) {
   if ( @{$ip{$ip}} > 1 ) {
      $duplicate_ip .= join ('', @{$ip{$ip}}) . "\n\n";

   }
}
#print "\nDuplicate hostnames with IP's\n";
foreach my $host ( sort keys %host ) {
      if ( @{$host{$host}} > 1 ) {
            my ($ip) = $host{$host}[0] =~ /^#?([\d.]+)/;
            unless ( @{$ip{$ip}} > 1 ) {
                  $duplicate_host .= join('', @{$host{$host}}) . "\n\n";
            }
      }
}

my $email_msg = <<EMAIL_MSG;
The following entries in the host file are duplicates
either by IP address or by hostname.
\n
************Duplicate IP addresses**************:
\n
$duplicate_ip
************Duplicate Hostnames*****************:
\n
$duplicate_host
EMAIL_MSG
print $email_msg;
my $email = MIME::Lite->new(
                          From => 'xxx@xxx.com',
                          To => 'xxx@xx.com',
                          Cc => 'xxy@xx.com,xxz@xx.com',
                          Subject => 'Host file duplicates',
                            Data => $email_msg
                            );
if ($duplicate_ip || $duplicate_host) { 
$email->send } #send email if duplicate found

perl scriptname e

my $option = $ARGV[0];