sub get_sub_dirs {
  use File::Spec; # so we don't have problems with
                  # platforms which use odd path
                  # seperators.
  my($path) = @_;

  my @dirs;
  
  opendir(DIR, $path) or die "Cannot open $path: $!\n";

  @dirs = grep {
     # not . or ..
      !/\A\.{2}\z/
         # XXX: Won't work on OSes where
         # normal directories can be called
         # '.' or '..' (e.g. MacOS)? 
    and
      # is a directory
      -d File::Spec->catfile($path, $_); 
         # (using catfile no chdir is needed;
         # we just get the full pathname of 
         # the file in question.)
  } readdir DIR;

  closedir DIR;

  return @dirs;
}