${${${$_[0]}[0]}[1]}{"dog"} = 15;

##</code><code>##

#! /usr/bin/perl

use strict;
use warnings;

use Data::Dumper;
$Data::Dumper::Indent = 2;

my $data;
$data->[0][0][0]{dog} = 15;

print Dumper $data;

##</code><code>##

$VAR1 = [
          [
            [
              {
                'dog' => 15
              }
            ]
          ]
        ];