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

my $ifile = shift;

open IFILE, '<', "$ifile" || die "Couldn't open file: $!";
open OFILE, '+>', 'new-data' || die "Couldn't open outfile: $!";

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

close IFILE;
close OFILE;