About the error messages

The errors about Global symbol <insert var here> are coming from the strict module. Any variable that you want to use must be declared in one of a few ways. Namely you can do

use vars qw(@some $vars %in_here);
# or you can do
my %variable;
# or even
local $some_var;
[download]

Each one has its own usage, and there are some gotchas. See your perl documentation about them

The error Multidimensional syntax $zone, $root not supported at ./ptr.pl line 24. is stating that the syntax of your line simply is not correct. What you are handing the readfh method is a scalar and then an anonymous array with 2 elements the first being nothing and the second being $root (which is not shown in your code, so I assume doensn't exist).

The documentation for that module isnt the best, but I will look over the source and see if I can't help out a touch more. Welcome to Perl :)

Update:Ok so there were a few isues, and looking over the source here are the issues.

#!/usr/bin/perl -w

$| = 1;

use strict;
use File::Find;
use FileHandle;
use Net::DNS::ZoneFile;

my $base    = "/chroot/named/master/arpa/in-addr/68/168";
my $out_dir = "/var/tmp/ptr";

find(\&wanted, $base);
exit;

sub wanted {
   return unless ( -f "$File::Find::name" and $File::Find::name !~ m!/
+com/! );
   return unless ( -f "$File::Find::name" and $File::Find::name !~ m!/
+net/! );

# Here we get the rootdir as an argument to the wanted function
# then we are going to need to open it as a new filehandle
# so that the module can read it.
   my $root  = shift;
   my $zone  = new FileHandle "$File::Find::name", "r";
   my $out   = join('.', ( split('/', $File::Find::name) )[-1,-2,-3]);
   my $rrset = Net::DNS::ZoneFile->readfh($zone, $root);

# here you were printing to STDOUT, as opposed to OUT
# which is what I assumed you wanted to do.
   open(OUT, ">$out_dir/$out") or die "Cant create $out_dir/$out: $!\n
+";
   print OUT $_->string . "\n" for @$rrset;
   close(OUT);
}
[download]

This code works. Mainly the issue was the $root var is an optional argument to the readfh method. If you didn't define it, then it used the current directory as the base directory to look for data in. So taking it as an arg for the wanted cleared it right up.

Regards

use perl;