What you need to do is perform a zone transfer and extract all of the A records for the domain in question.

#!/usr/bin/perl

use Net::DNS;
use Socket;
use strict;

my $domain = shift || "foo.com";

# Create a resolver object
my $res = new Net::DNS::Resolver;

# Ask the local resolver what the name servers for the domain in
# question.
my @ns;
my $query = $res->query($domain, "NS")
    or die "query failed; ". $res->errorstring;

for my $rr ($query->answer) {
    next if $rr->type ne "NS";
    my $dotted_quad =
        join(".", (unpack("C4", gethostbyname($rr->nsdname))));
    print "Found name server ".$rr->nsdname." ($dotted_quad)\n";
    push @ns, $dotted_quad;
}
$res->nameservers(@ns);

# ok, now we do a zone transfer
my @zoneinfo = $res->axfr($domain)
    or die "query failed; ". $res->errorstring;

# now loop through the answers and print those that are A records
for my $rr (@zoneinfo) {
    next if $rr->type ne "A";
    print "Found ". $rr->name ." A ".$rr->address."\n";
}
[download]

An alternative method might be to process the output of the "nslookup" or "dig" commands.

Why not check out nmap at insecure.org? Something like that can help you especially if you want to check the security of those hosts. You can also catch machines which have been set up to be quiet on your network, something which I don't think I'd trust ping to do. I know it's kind of like asking for a match and being given a tanker full of gasoline so be careful with the stuff. You should be able to parse the output file.

Probably all you need to do is write your own script to ping a small company network for something short and sweet. But know that professional tools like those above are available.

if you are on the name server, you can parse the zone files.
if your machines are all on the same subnet, you can check the broadcast address.
you could do a zone xfer as someone else suggested.

you said you are trying to see "what machines are up." you might want to look into netsaint or big brother. both of those require you to have a list of your IPs to start out with, though. your question implies maybe you have dynamic ips?

you also said you had some scripts that were useful, but lacking. what point(s) are you stuck at?

The point I was stuck at was that I had as of yesterday used objects in Perl for the first time, and had not quite figured out the Tao of what I was doing.

I had tried some example scripts on how to use the DNS stuff and then had tried modifying them to see if I understood what they were doing and how to use them. So while I had figured out how to obtain my own hostname and resolve its ip address. I really couldn't find a way to do what I was attempting.

However, since then I have discovered CPAN, learned how to install modules, and found that the world of Perl was far bigger than I had first thought.

Thanks for responding, I appreciate it!

Well, thanks everyone for helping out! A special thank you to mugwumpjism, your script does exactly what I need. Plus I had to look up join and unpack so that I could learn what they did. =) Extra bonus!

I will look into those other programs that were suggested (no sense in reinventing the wheel!). However, it sounds like what I really need to do is go buy a book on DNS, right? This is an internship I'm doing at a company, as the dedicated programmer for their IS department. So perhaps I could have solved this problem with some more knowledge of DNS? For example, I have no idea what a zone transfer is, so I'm going to go look that up as well.