TL;DR

Streamlining Adding functions in Template::Perlish.

Less than six months ago I wrote Adding functions in Template::Perlish, describing a possible way to… well, adding functions in Template::Perlish, a module that reinvents the good old template expansion wheel.

Since then, of course, I had a bug in the head to make it as easy as possible. Because, you know, I’ve been needing this for some time.

There’s been a bit of refactoring of the sections where other functions are injected since a long time, eventually resulting in a very compact change (in the right place):

# custom functions to be injected
if (defined(my $custom = $self->{functions})) {
   push @code, map {
      "   local *$_ = \$self->{functions}{$_};\n"
   } keys %$custom;
}

That’s it: it’s possible to pass a functions reference to a hash of name/sub pairs, and this will be temporarily injected in the template’s visibility as directly-callable functions. This also works in render(), the one-stop-shop for expanding templates.

Here’s an example:

use Template::Perlish 'render';

my $template = <<END_OF_TEMPLATE;
- variable<[% foo %]>
- missing<[% galook %]>
- function<[%= baz() %]>
- missing-function<[%= eval { missing() } or 'missing!' %]>
END_OF_TEMPLATE

my $processed = render(
   $template,
   {foo => 'bar'},    # variables
   {                  # options
      functions => {  # THE NEW STUFF!
         baz => sub { return 42 },
      },
   },
);

Output:

- variable<bar>
- missing<>
- function<42>
- missing-function<missing!>

As already pointed out in the docs, this module will not prevent anyone from shooting into their foots. I mean, it literally supports execution of arbitrary Perl code. Hence, use it only after carefully understanding the risk.

Stay safe!