#!/usr/bin/perl
use warnings;
use strict;

# takes ref to zero-or-more levels deep nested hash structure
# returns list of array refs for each leaf containing, top down, the keys
# to reach the node followed by the leaf value

sub leaves {
    my $node = shift;
    if (ref $node eq 'HASH') {
        my @leaves;
        for my $key (keys %$node) {
	    push @leaves, map [$key, @$_], leaves($node->{$key});
        }
        @leaves;
    } else {
        [$node];
    }
}

# takes ref to nested hash structure and list of top-down keys to traverse
# returns reference to to desired node

sub find_node_ref {
    my $noderef = \$_[0];
    shift;
    $noderef = \($$noderef->{$_}) for @_;
    $noderef;
}

our @in;
our $out;
$in[0]{foo}{bar}{baz} = 'bag';
$in[0]{foo}{fuw} = 'fu';
$in[1]{foo}{gar} = 'weeble';
$in[2]{foo}{bar}{baz} = 'bog';

for (my $idx = 0; $idx < @in; ++$idx) {
    next if not defined $in[$idx];
    for my $leaf (leaves($in[$idx])) {
        my $value = pop @$leaf;
        my $node = find_node_ref($out, @$leaf);
        $$node = [] unless defined $$node;
        $$node->[$idx] = $value;
    }
}

use Data::Dumper;
print Dumper \@in;
print Dumper $out;