Hi Elijah_A:

I believe the problem might be your source file. Are you sure it is a real BIND zone? Your example does not have a SOA record, which might be ok for your scenario.

On my side, the code below (slight modification of yours)...

#!/usr/bin/perl

use strict;
use warnings;
use Net::DNS;
use Net::DNS::ZoneFile;

my $rrset = Net::DNS::ZoneFile->readfh(*DATA);

print "Just read:\n";
print $_->string, "\n" for @$rrset;
push @$rrset, new Net::DNS::RR "3 7200 IN PTR gov.ph.";

foreach (@$rrset)
{
    next unless $_->type eq 'SOA' and $_->class eq 'IN';
    $_->serial($_->serial + 1);
}

print "After adding one to the SOA's serial:\n";
print $_->string, "\n" for @$rrset;

__DATA__
; Sta. Magdalena, Sorsogon
; Created by GovPh: Fri Aug  6 13:02:54 2004
stamagdalena IN NS ncc.xx.gov.ph
             IN NS ncc.xx.gov.ph
[download]

Produces the following output...

Just read:
stamagdalena.   0       IN      NS      ncc.xx.gov.ph.
stamagdalena.   0       IN      NS      ncc.xx.gov.ph.
After adding one to the SOA's serial:
stamagdalena.   0       IN      NS      ncc.xx.gov.ph.
stamagdalena.   0       IN      NS      ncc.xx.gov.ph.
3.      7200    IN      PTR     gov.ph.

I would check the source file for extraneous characters. For the record, this is what I'm running on my side:

$ perl -MNet::DNS::ZoneFile -e 'print $Net::DNS::ZoneFile::VERSION, "\n"'
1.10
$ perl -v | egrep darwin
This is perl, v5.8.1 built for darwin