if (template address exists) {
    include template
} else {
    include other template
}
##</code><code>##

sub template_exists {
    my ($self, $file) = @_;
    my $path = $self->config->template_path;
    return 1 if grep { -e && -f && -r } map { "$_/$file" } @$path;
    return;
}
##</code><code>##

[% FOREACH thing = collection %]
    [% template = factory.template_exists("list/types/${thing.type}.html") ?
        "list/types/${thing.type}.html" : 
        "list/types/default.html" 
    %]
    [% INCLUDE $template %]
[% END %]