my $basedir = '/top/of/the/tree/';

opendir( ARTISTS, $basedir )
  or die "Can't read from $basedir : $!";

foreach my $artist ( readdir(ARTISTS) ) {
  next if (-D "$basedir/$artist" or $artist =~ m/^[.]*$/);

  opendir( ALBUMS, "$basedir/$artist" )
    or warn "Can't read from $basedir/$artist : $!"
    and next;

  foreach my $album ( readdir(ALBUMS) ) {
    next if (-D "$basedir/$artist/$album" or $album =~ m/^[.]*$/);

    opendir ( TRACKS, "$basedir/$artist/$album" )
      or warn "Can't read from $basedir/$artist/album : $!"
      and next;

    foreach my $track ( readdir(TRACKS) ) {
      next if ($track =~ m/^[.]*$/);

      ...

    }
  }
}