#!/usr/bin/perl

use 5.010;

use strict;
use warnings;

use Devel::Size qw [total_size];

my $size = 250_000;

my @fields = qw [chr start end symbol strand];
my %families;
my @structs = \my (%chr, %start, %end, %symbol, %strand);

foreach my $key (1 .. $size) {
    $families{$key}{$_} = undef for @fields;  
    $$_{$key} = undef for @structs; 
}

my $s1 = total_size \%families; 
my $s2 = 0; 
   $s2 += total_size $_ for @structs;

printf "Big hash: %d Mb\n", $s1 / (1024 * 1024);
printf "More hashes: %d Mb\n", $s2 / (1024 * 1024);
printf "Savings: %.0f%%\n", 100 * ($s1 - $s2) / $s1;

__END__
Big hash: 71 Mb
More hashes: 61 Mb
Savings: 14%