$ cat /tmp/t.pl ; perl /tmp/t.pl 
#! /usr/bin/env perl
use strict;
use warnings;
use 5.020;


use Devel::Size qw( size total_size );

my $cache_hash = {};
$cache_hash->{0x0} = 2;
say size( $cache_hash );            # 185
say total_size( $cache_hash );      # 209

my $cache_array = \my @cache_array;
$cache_array->[0x0] = 2;
say size( $cache_array );           # 8_912_944
say total_size( $cache_array );     # 8_912_968

__END__