I know that our editor-in-chief this year, the amazing cromedome, is hoping for some deep wisdom here about why and how I created Dancer2::Template::Handlebars.

He's going to have to get used to disappointment.

I realized a while back that, after nearly 20 years of writing Perl, I didn't have a single module on CPAN. It seemed to me that something simple-ish would be a good idea, just so I could work out the workflow, and I'd been playing around with some templating using Handlebars for another project of mine. To make it even easier, the underling Text::Handlebars was already present, and our clever colleague Yanick had already written Dancer::Template::Handlebars, from which I could crib some code as needed.

All the bits were in place, it was just up to me to learn the bits and pieces of creating, testing, and submitting a module. But why this one?

Why you should like Handlebars, and use it

Handlebars, like Template Toolkit and many others, can take objects handed to it from Dancer2's template-processing system, and insert data into pages, at your direction. So, if you have a list of people objects with names, you can get a list of them:

{{#each people}}
    {{ lastname }}, {{ firstname }}

Handlebars also supports "partials", subtemplates you might want to call, similar in behavior to TT's INCLUDE or PROCESS tools. You can even dynamically call a partial by referencing a variable name containing the name of the partial!

What sets Handlebars apart from Template Toolkit is its model of "helpers." There are a few built-in helpers, like #each and #with, which create loop iterators, #if and #unless that create conditionals, and a lookup log helper, which provide data access and logging, respectively. But everything else you might want to do is a helper you must include or write. Writing them is relatively straightforward JavaScript, like so:

Handlebars.registerHelper('loud', function (aString) {
        return aString.toUpperCase()

Then in your template,

{{loud lastname }}, {{ firstname }}

And for me, you'd get HOLLOWAY, Ruth.

By default, the "double-stache" construct used in Handlebars templates will escape your HTML, which may not be what you want. If you have a bit of HTML your Dancer application is generating, or storing in a database, you can tell Handlebars to skip the escaping with a "triple-stache": {{{ generated_html_field }}}.

For me, at least, the aesthetics of Handlebars are clean and easy to read, and the helper format creates a nice easy-to-read layout. It's lightweight, and easy to read and code. Is it the next "best thing since sliced bread?" Not at all. But it's a good templating language, that some developers might find useful.

So, how did I turn that into a plugin for Dancer2?

As I mentioned before, Yanick had already done a Dancer plugin for Handlebars. He had also created Dancer::Template::Mustache, and ported that to Dancer2::Template::Mustache, so I had a template to go by.

I mercilessly plagarized. That's how I did it. I even told Yanick that I was plagarizing, and he just encouraged me. Then I used Dist::Zilla to get it ready and release it.

If you've got a Dancer plugin that you'd like to see ported to Dancer2, I strongly recommend this trick; take a look at a similar module where someone has already done that migration, and go and do likewise. It's not hard!


This article has been written by D Ruth Holloway (GeekRuthie) for the Perl Dancer Advent Calendar 2020.

Copyright & License

Copyright (C) 2020 by D Ruth Holloway (GeekRuthie). This work is licensed under a Creative Commons Attribution 4.0 International License.