#!/usr/bin/perl

use strict;
use warnings;

my %hoh;

$hoh{'FILENAME1'}{'A'}{'weight'}=3000;
$hoh{'FILENAME1'}{'A'}{'intensity'}=2;

$hoh{'FILENAME1'}{'B'}{'weight'}=4000;
$hoh{'FILENAME1'}{'B'}{'intensity'}=3;

$hoh{'FILENAME2'}{'D'}{'weight'}=2000;
$hoh{'FILENAME2'}{'D'}{'intensity'}=7;

$hoh{'FILENAME2'}{'C'}{'weight'}=5000;
$hoh{'FILENAME2'}{'C'}{'intensity'}=3;

$hoh{'FILENAME3'}{'C'}{'weight'}=1000;
$hoh{'FILENAME3'}{'C'}{'intensity'}=4;

$hoh{'FILENAME3'}{'A'}{'weight'}=6000;
$hoh{'FILENAME3'}{'A'}{'intensity'}=3;

# Let's flatten %hoh out, and store what we care about in this
# array of references to arrays.
my @by_weights = ();

# Populate @by_weights.
for my $key_in_hoh (keys %hoh) {
    for my $key_in_fin (keys %{$hoh{$key_in_hoh}}) {
        for my $key_in_let (keys %{$hoh{$key_in_hoh}{$key_in_fin}}) {
            # We'll fix the intensity value later.
            if ($key_in_let eq 'weight') {
                push @by_weights, [ $key_in_let,
                                    $hoh{$key_in_hoh}{$key_in_fin}{$key_in_let},
                                    'intensity',
                                    0, # Fill in correct value later.
                                    $key_in_fin,
                                    $key_in_hoh,
                                  ];
            }
        }
    }
}

# Correct the intensity values.
for (@by_weights) {
    my ( $key_in_hoh, $key_in_fin ) = ( $_->[5], $_->[4] );
    $_->[3] = $hoh{$key_in_hoh}{$key_in_fin}{intensity};
}

# Now, sort by weight.
@by_weights = sort { $a->[1] <=> $b->[1] } @by_weights;

for (@by_weights) {
    print "${$_}[0]: ${$_}[1] $_->[2]: ${$_}[3] filename: $_->[5]\n";
}