use strict;
use DateTime;
use Template;

my $config = {};
my $template = Template->new($config);
my $input = \'[% calendar.ymd(".") %]';

# process input template, substituting variables
$template->process($input, { calendar => DateTime->now })
    or die $template->error();

##</code><code>##

undef error - Cannot compare a datetime to a regular scalar (2005-02-28T21:51:58 / Template::Stash=HASH(0x2048a14)) at c:/perl/site/5.8.5/lib/Template/Stash.pm line 582