Handlebars:
Template
<div class="entry">
{{#unless license}}
<h3 class="warning">WARNING: This entry does not have a license!</h3>
{{/unless}}
</div>
Preparation-Script
// Handlebars.registerHelper('loud', function(string) {
//    return string.toUpperCase()
// });
Input
{}
Output
<div class="entry">
<h3 class="warning">WARNING: This entry does not have a license!</h3>
</div>