#!/usr/bin/perl
use strict;
use warnings;

use Cwd;
use Getopt::Std;

my %opts;
getopts('d:', \%opts);
my $start_dir = $opts{d};
$start_dir = getcwd() unless defined ($start_dir);

listDir($start_dir);
print ("\n\nfinished.\n\n");

sub listDir {
    my $thisdir = $_[0];
    print "\n$thisdir:\n";

    opendir THISDIR, $thisdir;
    my @allentries = readdir THISDIR;
    my @directories = sort grep(-d "$thisdir/$_" && !/^\.\.?$/, @allentries);
    closedir THISDIR;

    foreach my $entry (@allentries) {
        print "\t$entry\n";
    }
    foreach my $entry (@directories) {
        chomp($entry);
        listDir("$thisdir/$entry");
    }
}