Some more details: in this post someone asked how to "take strings like:"

/file.txt
/a/file.txt
/a/b/c
/a/b/c/file.txt
/z/m/w/file.txt
[download]

and "produce something like:"

%dir_hash(
    'file.txt' => '',
    'a' => {
        'file.txt' => '',
        'b' => {
            'c' => {
                'file.txt'
[download]

In my reply I pointed out that there should be a module designed for exactly this kind of things, which I still fail to remember. (Hey, anyone here? Update: It's Data::Diver, thanks to tye!) But first of all I provided a minimal example to accomplish not exactly the same task, but a very close one; the original code is as follows:

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

my %dirhash;
while (<DATA>) {
    chomp;
    my $last=\%dirhash;
    $last=$last->{$_} ||= {} for split qr|/|;
}

print Dumper \%dirhash;

__END__
/file.txt
/a/file.txt
/a/b/c
/a/b/c/file.txt
/z/m/w/file.txt
[download]

In it I have to compensate for perl not autovivifying in this case. Then Brian McCauley provided an alternative way, precisely suggesting that one do

my $last=\\%dirhash;
$last=\$$last->{$_} for split qr|/|;
[download]

Instead, which is the Autovivification trick I'm "advertising" here.