The answer depends on what you want: ascii or html table output (consider embperl here) or just a suitable data structure before starting to think about output formatting issues..

As for the data structure itself, how about a a hash := anonymous hash | filename (as key use the basename of the dir | file; read as EBNF). In case of a reference, you're dealing with a directory (inner node of tree), otherwise with a file (leaf). Similar approach if you prefer an array instead.

A variant: KISS - is it suitable to use just the full dirpath as key? Then you can use a non-recursive approach: a hash of anonymous arrays.

cu
Peter

Updates: do check man perlref / perlreftut.