And hashes can be more efficient if there are holes in the index.

use strict;
use Devel::Size qw(total_size);

my %hash = ( 0 => 3,
             1 => 7,
             2 => 5,
             3 => 0,
             20202 => 2,
           );

my @vals = qw(3 7 5 0);
$vals[20202] = 2;

print 'T1: ', total_size(\%hash),"\n";
print 'T2: ', total_size(\@vals),"\n";

[waswas:/var/tmp] waswas% perl hah
T1: 291
T2: 131228
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