Ok I just finished studying this :) I understand everything now and I will read on subs, map and printf. Thank you so much! :)

edit: Actually I was thinking I'd like to make it a bit more "organised" especially in case I add more subfolders in the future, so I made this slight change (nothing really, just specified the subdirectories in the beginning). It looks like it's correct and the result is what I want - sorry, just getting paranoid that I might have messed the subroutine up, that's the only reason why I'm posting this tiny change.

 my @dirs = (
    dir_tree( 'AB', 6, 1, 2 ),
    dir_tree( 'BC', 6, 1, 2 ),
);

my @subdirs = (
   dir_tree( 'F', 6, 1, 5 ),
);


for my $dir (@dirs) {
    for my $subdir (@subdirs) {
        print "/results/$dir/$subdir \n";
    }
}
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