#!/usr/local/bin/perl -w

use Net::hostent;

my @ips = qw( 1.2.3.4 5.6.7.8 );    # Use your own IPs
my %hosts;
foreach my $ip ( @ips ) {
  my $info = gethost( $ip );        # Returns an object
  unless( $info ) {
    warn( "gethost failed for [$ip] : $! $?" );
    next;
  }
#  ...access other interesting bits of $info if you want...
  $hosts{$ip} = $info->name();      # Just want the name
}

# Ta da. The %hosts hash now contains a set of ip => host mappings.
foreach my $ip ( keys %hosts ) {
  print "The hostname of IP address [$ip] is [$hosts{$ip}]\n";
}