__PACKAGE__->tt_config(
    TEMPLATE_OPTIONS => {
        # same as above, plus:
        CONSTANTS       => {
            menu    => [
                { text => 'Foo',
                  link => 'foo.html', },
                { text => 'Bar',
                  link => 'Bar.html', },
            ],
            foo     => 'foo!',
        },
    },
);

# main_menu.tmpl
<ul>
    <li>[% constants.foo %]</li>
[% FOREACH constants.menu %]
    <li><a href="[% link %]">[% text %]</a></li>
[% END %]
</ul>