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

my $ifile = shift;
my $ofile = 'new_data';

open my $ifh, '<', $ifile
   or die "Couldn't open DNS file \"$ifile\": $!\n";
open my $ofh, '>', $ofile
   or die "Couldn't create output file \"$ofile\": $!\n";

while (my $line = <$ifh>) {
   # is the line an MX record?
   if ($line =~ /^@.*mail(\d+)/xms) {
      # is it less than or equal to 8?
      if ($1 <= 8) {
         print $ofh $line;
      }
   }
   # print everything else to the new file
   else {
      print $ofh $line;
   }
}

##</code><code>##

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

#
# Usage:
#    fixdns infile > outfile
#
# Usage for in place editing:
#    perl -i fixdns dnsfile
#

while (<>) {
   # is the line an MX record?
   if (/^@.*mail(\d+)/xms) {
      # is it less than or equal to 8?
      if ($1 <= 8) {
         print;
      }
   }
   # print everything else to the new file
   else {
      print;
   }
}