package MyApp::TT::Plugin::BBCodeFilter;

use base qw(Template::Plugin::Filter);

use Parse::BBCode;

my $bbc;
sub init {
  my $self = shift;

  my $name = $self->{_CONFIG}->{name} || 'bbcode';
  $self->install_filter($name);

  $bbc = Parse::BBCode->new;

  return $self;
}

sub filter {
  my ($self, $text) = @_;

  $text = $bbc->render($text);

  return $text;
}

1;

##</code><code>##

my %tpl_settings = (
                    ...
                    PLUGIN_BASE => 'MyApp::TT::Plugin',
                    ...
                   );
my $tt = Template->new(%tpl_settings);

##</code><code>##

[% USE BBCodeFilter -%]
<p>[% (comments || '(No Comments)') | bbcode %]</p>