/file.txt
/a/file.txt
/a/b/c
/a/b/c/file.txt
/z/m/w/file.txt

##</code><code>##

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

##</code><code>##

#!/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

##</code><code>##

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