c:\@Work\Perl\monks>perl -wMstrict -le
"my @ra = (
   '/Volumes/WD/Not Migrating/Music/Ana Tijoux',
   '/Volumes/WD/Not Migrating/Music/Eminem/Ana Tijoux/Luchin',
   '/Volumes/WD/Not Migrating/Music/Eminem/Ana Tijoux/Luchin/Luchin.m4a',
   );
 print qq{'$_'} for @ra;
 ;;
 my $dir_level = qr{ / [^/]+ }xms;
 ;;
 my $n = 4;
 s{ \A (?: $dir_level){$n} / }{}xms for @ra;
 print qq{'$_'} for @ra;
 ;;
 for my $s (@ra) {
   my $n_fs = $s =~ tr{/}{};
   my $indent = '   ';
   printf qq{%s'$s' \n}, $indent x $n_fs;
   }
"
'/Volumes/WD/Not Migrating/Music/Ana Tijoux'
'/Volumes/WD/Not Migrating/Music/Eminem/Ana Tijoux/Luchin'
'/Volumes/WD/Not Migrating/Music/Eminem/Ana Tijoux/Luchin/Luchin.m4a'
'Ana Tijoux'
'Eminem/Ana Tijoux/Luchin'
'Eminem/Ana Tijoux/Luchin/Luchin.m4a'
'Ana Tijoux'
      'Eminem/Ana Tijoux/Luchin'
         'Eminem/Ana Tijoux/Luchin/Luchin.m4a'