#!/usr/bin/perl
use strict; use warnings;
use YAML::XS;
use Data::Dumper;
my $data;
{local $/;$data = <DATA>};
print Dumper mergekeys( Load $data );

sub mergekeys
{
    my ($ref) = @_;
    my $type = ref $ref;
    if ($type eq 'HASH')
    {
        my $tmphref = $ref->{'<<'};
        if ($tmphref)
        {
            die "Merge key does not support merging non-hashmaps"
                unless (ref $tmphref eq 'HASH');
            my %tmphash = %$tmphref;
            delete $ref->{'<<'};
            %$ref = (%tmphash, %$ref);
        }
        mergekeys($_) for (values %$ref);
    }
    elsif ($type eq 'ARRAY')
    {
        mergekeys($_) for (@$ref);
    }
    return $ref;
}