while (my $invoice = $sth->fetchrow_hashref) {

	my $tmp = $invoice->{amazon_order_id};
       $tmp =~ s/ \(\d+\)//; # get rid of (0) (1) etc at the end of the id, as we dont need it here
	print qq|GOT: $invoice->{amazon_order_id} ($tmp) \n|;
	if ($invoices->{$tmp}) {
		print STDERR "TEST: " . ref($invoice_items->{$tmp}) . "\n";
		push @{$invoice_items->{$tmp}} = {
			name => 	$invoice->{product_name},
			qty =>  	$invoice->{quantity_shipped},
			amount => 	$invoice->{item_price},
			total =>    $invoice->{item_price} * $invoice->{quantity_shipped},
		};
		print STDERR "added.. \n";
	} else {
		$invoices->{$tmp} = $invoice;
		push @{$invoice_items->{$tmp}}, {
				name => 	$invoice->{product_name},
				qty =>  	$invoice->{quantity_shipped},
				amount => 	$invoice->{item_price},
				total =>    $invoice->{item_price} * $invoice->{quantity_shipped},
		};

		print Dumper($invoice_items);
	}
}

##</code><code>##

TEST: ARRAY
Not an ARRAY reference at make.cgi line 34.

##</code><code>##

push @{$invoice_items->{$tmp}} = {
   ... vals
}