# Yuri    # 19.02.2013    # this script accepts range of IP addresses to do PTr resolving for    # the range has to be in this format: startIp-endIp.startIp-endIp.startIp-endIp.startIp-endIp.    # Only answers are printed, i.e. if there is no answer  nothing is printed    use warnings;    use strict;    use Net::DNS ;    my $res = Net::DNS::Resolver->new();      my $input = shift ;         $input =~ /(.+)-(.+)\.(.+)-(.+)\.(.+)-(.+)\.(.+)-(.+)/ ;         print "Resolving ptrs for the following range: $input\n" ;         print "Started working at: " . scalar gmtime . "\n" ;         my ($oct1_start,$oct1_end,$oct2_start,$oct2_end,$oct3_start,$oct3_end,$oct4_start,$oct4_end) = ($1,$2,$3,$4,$5,$6,$7,$8) ;     foreach my $oct1 ($oct1_start..$oct1_end) {       foreach my $oct2 ($oct2_start..$oct2_end) {         foreach my $oct3 ($oct3_start..$oct3_end) {           foreach my $oct4 ($oct4_start..$oct4_end) {       my $answer = $res->query("${oct1}.${oct2}.${oct3}.${oct4}") ;     if (defined $answer) {    my @ptr = $answer->answer;    foreach my $record_ptr (@ptr) {    #print " NEw " . $record_ptr->print ;     my $str = substr($record_ptr->string,rindex($record_ptr->string,'R')+1) ;     print "$oct1.$oct2.$oct3.$oct4  "  . $str . "\n";    }    }    } } }}      print "Run completed at: " . scalar gmtime . "\n" ;