#... yada yada ...
my %ips = (
   ours => {
      24.56.102.10 => 'ns1.t',
   },
   theirs => {
      68.168.192.17 => 'ns1.a',
   },
);

my @recs = nslookup(
   type   => "NS",
   domain => $domain,
);

ours(\%ips, \@recs);
 
# .. yada yada ..

sub ours {
   my($ip, $recs) = @_;

   for ( @$recs ) {
      if ( $ip->{ours}{$_} ) {
         print OUT "$_\n";

      } elsif ( $ip->{theirs}{$_} ) {
         print OUT1 "$_\n";

      } else {
      # do we care about this case?
      }
   }
}