use strict;
use warnings;

use Data::Dumper;

my %fields = (
	version1 => {
		1 => 'Field 1',
		2 => 'Field 2',
		3 => 'Field 3',
	},
	version2 => {
		1 => 'Field 1',
		2 => 'Field 2',
		3 => 'Field 3',
		4 => 'Field 4',
	},
	version3 => {
		1 => 'Field 1',
		2 => 'Field 2',
		3 => 'Field 3',
		4 => 'Field 4',
		5 => 'Field 5',
	},
	version4 => {
		# What if version4 is exactly the same as version3.
		# How do I just make version4 point to verson3?
	},
);

print STDERR "fields Dump1:\n", Dumper(\%fields), "\n";

$fields{version4} = $fields{version3};

print STDERR "fields Dump2:\n", Dumper(\%fields), "\n";