sub optional_unique_properties {
    qw(
        class  completed  created  description  dtstamp
        dtstart  geo  last-modified  location  organizer
        percent-complete  priority  recurrence-id  sequence  status
        summary  uid  url

        due duration
    );
}

##</code><code>##

use Data::Dumper;
use strict;
use Data::ICal::Entry::Todo;

my $vtodo = Data::ICal::Entry::Todo->new();
print Dumper($vtodo->optional_unique_properties());

##</code><code>##

$VAR1 = 'class';
$VAR2 = 'completed';
$VAR3 = 'created';
$VAR4 = 'description';
$VAR5 = 'dtstamp';
$VAR6 = 'dtstart';
$VAR7 = 'geo';
$VAR8 = 'last-modified';
$VAR9 = 'location';
$VAR10 = 'organizer';
$VAR11 = 'percent-complete';
$VAR12 = 'priority';
$VAR13 = 'recurrence-id';
$VAR14 = 'sequence';
$VAR15 = 'status';
$VAR16 = 'summary';
$VAR17 = 'uid';
$VAR18 = 'url';
$VAR19 = 'due';
$VAR20 = 'duration';

##</code><code>##

use base qw/Data::ICal::Entry/;

##</code><code>##

sub new {
    my $class = shift;
    my $self  = {
        properties => {},
        entries    => [],
    };
    bless $self, $class;
    return $self;
}