> This is not possible.

You've been given a solution by haukex in Re: 5.24 -> 5.28 -- what has changed in autovivification?.

Do you need more details? Here's an example:

#! /usr/bin/perl
use warnings;
use strict;
use feature qw{ say };

use Data::Diver qw{ Dive };
use Data::Dumper;

my $h1 = {};
my $h2 = {a => {b => {c => 42}}};

for my $h ($h1, $h2) {
    say "Found $h->{a}{b}{c}" if Dive($h, qw( a b c ));
}
print Dumper $h1, $h2;
[download]

Output:

Found 42
$VAR1 = {};
$VAR2 = {
          'a' => {
                   'b' => {
                            'c' => 42
                          }
                 }
        };
[download]