my @arr = (
  { 'path' => '/c/', dir => '/' },
  { 'path' => '/c/a1.mp3', 'file' => 1, 'dir' => '/c' },
  { 'path' => '/c/a2.mp3', 'file' => 1, 'dir' => '/c' },
  { 'path' => '/c/bb/aa1.mp3', 'file' => 1, 'dir' => '/c/bb' },   # this is /c/bb
  { 'path' => '/c/bb/aa2.mp3', 'file' => 1, 'dir' => '/c/bb' },   # this is /c/bb
  { 'path' => '/c/bb/', 'dir' => '/c' },
  { 'path' => '/c/cc/', 'dir' => '/c' },
  { 'path' => '/c/aa/', 'dir' => '/c' }
);