Text Templates in Perl

Perl offers built-in support for creating dynamic content or showing customized output to the user with the Text::Template module. This module provides a simple way to generate text using templates.

use strict;
use warnings;
use Text::Template;
use Data::Dumper;

# We can create a new template and parse its body from a string.
# Templates are a mix of static text and expressions enclosed in
# {$...} that are used to dynamically insert content.

my $t1 = Text::Template->new(
    TYPE => 'STRING',
    SOURCE => 'Value is {$_}',
);

# By "filling in" the template we generate its text with
# specific values for its expressions.
print $t1->fill_in(HASH => { _ => "some text" });
print $t1->fill_in(HASH => { _ => 5 });
print $t1->fill_in(HASH => { _ => Dumper(["Perl", "Python", "Ruby", "PHP"]) });

# If the data is a hash we can use the {$variable} syntax to access
# its keys.

my $t2 = Text::Template->new(
    TYPE => 'STRING',
    SOURCE => 'Name: {$name}',
);

print $t2->fill_in(HASH => { name => "Jane Doe" });
print $t2->fill_in(HASH => { name => "Mickey Mouse" });

# if/else provide conditional execution for templates. A value is considered
# false if it's undefined, an empty string, 0, or an empty list.

my $t3 = Text::Template->new(
    TYPE => 'STRING',
    SOURCE => '{if $_}yes{else}no{/if}',
);

print $t3->fill_in(HASH => { _ => "not empty" }), "\n";
print $t3->fill_in(HASH => { _ => "" }), "\n";

# To loop through arrays, we can use Perl's foreach construct within
# the template.

my $t4 = Text::Template->new(
    TYPE => 'STRING',
    SOURCE => 'Range: {foreach $item (@$_) {$item } }',
);

print $t4->fill_in(HASH => { _ => ["Perl", "Python", "Ruby", "PHP"] }), "\n";

When you run this script, you should see output similar to this:

$ perl templates.pl
Value is some text
Value is 5
Value is $VAR1 = [
          'Perl',
          'Python',
          'Ruby',
          'PHP'
        ];

Name: Jane Doe
Name: Mickey Mouse
yes
no
Range: Perl Python Ruby PHP

In this Perl version:

We use the Text::Template module for templating.
Template variables are enclosed in {$...} instead of {{...}}.
We use fill_in method to render templates instead of Execute.
Conditional statements use {if}...{else}...{/if} syntax.
For looping, we use Perl’s foreach construct directly in the template.

Note that Perl’s Text::Template is more flexible than Go’s text/template in some ways, as it allows arbitrary Perl code in the templates. This can be powerful but also potentially dangerous if used with untrusted input.

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Text Templates in Perl