#!/usr/bin/perl

use strict;

( @ARGV == 2 and -f $ARGV[0] )
    or die "Usage: $0  input.file  domain.to.comment.out\n";

my ( $in_file, $rem_domain ) = @ARGV;
open IN, "<", $in_file or die "$in_file: $!";
open OUT, ">", "$in_file.new" or die "$in_file.new: $!";

$/ = "\n}";     # input record separator is line-initial "}"

while (<IN>) {               # $_  contains a whole zone block
    if (/\W$rem_domain\W/) {
        s/^/#/;              # add initial comment to block
        s/\n/\n#/g;          # add comment after each "\n"
    }
    print OUT;
}