Here is my final code but I need help:

1. All duplicates IP are not going under "Duplicate IP" section. Like the folllwing example:

10.16.15.0 abcdefg0000 abcdefg0000
10.16.15.0 abcdefg0000 abcdefg0000

Should have gone to Duplicate IP, but it went under duplicate hosts.


2. if there are duplicates of device and IP
like follow:

#172.11.111.222 abc014i00def
#172.11.111.222 abc014i00def

the output went in both section "Duplicate IP" and "Deuplicate hosts" instead going one of the section.

3. Output not coming up with TAB in between the IP<>DeviceName<Restoftheinfo>

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, $host) = /^#?([\d.]+)\s+(\S+)/ ) {
push @{$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 $host ( keys %host ) {
if ( @{$host{$host}} > 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.
Duplicate IP addresses:
$duplicate_ip
Duplicate Hostnames:
$duplicate_host
EMAIL_MSG
print $email_msg;
my $email = MIME::Lite->new(
From => 'xxxx@xx.com',
To => 'xxxx@xx.com',
#Cc => 'yyyy@yy.com,xxzzz@zz.com',
Subject => 'Host file duplicates',
Data => $email_msg
);
$email->send