$hash{subdir 1}
  $hash{subdir 2}{subsubdir 2.1}
  $hash{subdir 2}{subsubdir 2.2}
  $hash{subdir 3}{subsubdir 3.1}
  $hash{subdir 3}{subsubdir 3.1}{subsubsubdir 3.1.1}
  $hash{subdir 3}{subsubdir 3.1}{subsubsubdir 3.1.2}
  $hash{subdir 3}{subsubdir 3.1}{subsubsubdir 3.1.3}