#!/usr/bin/perl -w
use strict;
use Socket;

my $logfile = 'hosts.txt';
open HOST, ">> $logfile" or die "Can't open $logfile: $!\n";

# The following snippet will unbuffer your filehandle
# so that data is written out immediately.
{ 
    my $ofh = select HOST;
    $| = 1;
    select $ofh;
}


for my $i ( 0 .. 255 ) {
    for my $j ( 0 .. 255 ) {
        for my $k ( 0 .. 255 ) {
            for my $l ( 0 .. 255 ) {

                my $address = "$i.$j.$k.$l";
                my $iaddr   = inet_aton( $address );
                my $name    = gethostbyaddr($iaddr, AF_INET) || '';
                chomp $name if $name;

                print "$address\t$name\n";
                print HOST "$address\t$name\n" or die "Can't print to $logfile: $!";
            }
        }
    }
}

close HOST or die "Can't close $logfile: $!";