while (<OLD>) {
   chomp;
   my @fields = split /,/;
   my $pc = $fields[0];   # get the first field
   $pc =~ s/"//g;         # get rid of the quotes
   if (! exists $old {$pc}) {
      # the new pc file has a pc which did not exist
      # in the old pc file
      print "new PC found: $pc\n";
   }
}
# and cleanup
close (OLD);
close (NEW);