#!/usr/bin/perl -w
use strict;
my %hash = (
	1 => 1,
	2 => { 3 => 4,
		5 => {
			6 => 7 },
		},
	8 => 9,
	10 => {},
);

my @stack;
push @stack, \%hash;
my $tree = '';
my $level = 0;

while (@stack) {
	my ($hash_ref, $keys_ref);
	if (ref($stack[-1]) eq 'ARRAY') {
		($hash_ref, $keys_ref) = @{ pop @stack };
		$level--;
	} else {
		$hash_ref = pop @stack;
		$keys_ref = [ sort { $b <=> $a } (keys %$hash_ref) ];
	}
	while (my $key = pop @{ $keys_ref }) {
		my $value = $hash_ref->{$key};
		if (ref($value) eq 'HASH') {
			$tree .= "\t" x $level . "$key => \n";
			push @stack, ([ $hash_ref, $keys_ref ], $value);
			$level++;
			last;
		} else {
			$tree .= "\t" x $level . "$key => $value\n";
#			print "on key $key, stack is ", $level, " levels deep.\n";
		}
	}
}
print $tree;