$singleton->{xml_filename} = $_[0];
$singleton->{hostlist}     = \@hostlist;

##</code><code>##

Dancer->new;     # invocant is "Dancer"
$obj->dance;     # invocant is $obj

##</code><code>##

my @components = @{ $config->{host}->{component} };
foreach (@components)
{
   push @hostList, $_->{component_name};
}

##</code><code>##

push @hostList,
   map { $_->{component_name} }
   @{ $config->{host}->{component} };

##</code><code>##

{
	package MyConfig;
	use Moose;
	use MooseX::Singleton;
	use XML::Simple;

	has xml_filename => (
		is         => 'ro',
		isa        => 'Str',
		required   => 1,
	);

	has _config => (
		is         => 'ro',
		isa        => 'Any',
		lazy_build => 1,
	);

	has hostlist => (
		is         => 'ro',
		isa        => 'ArrayRef',
		lazy_build => 1,
	);

	sub _build__config {
		my $self = shift;
		my $xml  = XML::Simple->new;
		$xml->XMLin($self->xml_filename, ForceArray => [ 'host', 'component' ])
			or die $!;
	}

	sub _build_hostlist {
		my $self = shift;
		my @hostlist = 
			map { $_->{component_name} }
			@{ $self->_config->{host}[0]{component} };
		return \@hostlist;
	}
}

my $config   = MyConfig->new(xml_filename => "myconfig.xml");
my @hostlist = @{ $config->hostlist };

print "@hostlist";