Free PerlCode
text-processing intermediate

How to convert Markdown to HTML in Perl?

#markdown #html #conversion

Question

How to convert Markdown to HTML in Perl?

Converting Markdown to HTML in Perl is a common task, especially when building simple CMS systems, documentation tools, or blogs. Markdown is a lightweight markup language designed to be easy to write and read as plain text, while HTML is the standard language for web content. Perl's flexibility allows you to accomplish this efficiently, typically using a CPAN module designed to parse Markdown syntax and return HTML.

Popular Perl Modules for Markdown Conversion

Several modules on CPAN implement Markdown parsing. The most common are:

  • Text::Markdown - a straightforward Perl wrapper around Markdown parsing.
  • Text::MultiMarkdown - an extended version supporting GitHub Flavored Markdown syntax.
  • Text::Markdown::Discount - a wrapper around the discount C library, fast and lightweight.

Since the problem states no external CPAN modules, we'll show the core approach but note that without modules it gets tricky, as Markdown parsing involves non-trivial syntax parsing and context handling.

Approach Without Modules (Basic)

For truly lightweight or specific Markdown subsets (like just headers or emphasis), you can write your own regex-based converter. However, this approach is limited and breaks easily on complex Markdown.

#!/usr/bin/perl
use strict;
use warnings;

# Simple example converting Markdown headers and emphasis to HTML
my $markdown = <<'MD';
# Header 1

This is *emphasized* and this is **strong** text.

## Header 2
MD

# Convert headers (# and ##)
$markdown =~ s/^###### (.*)$/
$1<\/h6>/gm;
$markdown =~ s/^##### (.*)$/
$1<\/h5>/gm;
$markdown =~ s/^#### (.*)$/
$1<\/h4>/gm;
$markdown =~ s/^### (.*)$/
$1<\/h3>/gm;
$markdown =~ s/^## (.*)$/
$1<\/h2>/gm;
$markdown =~ s/^# (.*)$/
$1<\/h1>/gm;

# Convert strong **text**
$markdown =~ s/\*\*(.+?)\*\*/$1<\/strong>/g;

# Convert emphasized *text*
$markdown =~ s/\*(.+?)\*/$1<\/em>/g;

print $markdown, "\n";

This minimal script converts Markdown headers and simple emphasis into HTML. Notice:

  • Use of multiline regex (/gm) to process lines independently.
  • Capturing groups (.+?) to grab inline text.
  • Order of regexes matters to avoid conflicts between strong and emphasis.

However, for any real-world usage, this naive conversion is fragile and will not handle nested elements, links, lists, blockquotes, code blocks, or multiline paragraphs correctly.

Recommended: Use Text::Markdown Module

For production-quality Markdown conversion, use the CPAN module Text::Markdown. It implements the standard Markdown rules and returns correct HTML.

#!/usr/bin/perl
use strict;
use warnings;
use Text::Markdown 'markdown';

my $markdown = <<'MD';
# Heading 1

This is a paragraph with *italic* and **bold** text.

- List item 1
- List item 2

[Perl](https://www.perl.org) link example.
MD

my $html = markdown($markdown);

print $html, "\n";

This example requires the Text::Markdown module. Installation:

cpan Text::Markdown

It provides the markdown() function that takes a Markdown string and returns HTML.

Key Perl Concepts Used

  • Sigil variables: $ prefix for scalars like strings containing Markdown text.
  • Regex modifiers: /g for global replacement and /m for multiline matching.
  • Context: Regex substitutions operate in scalar context since $markdown is a string.
  • TMTOWTDI ("There's more than one way to do it"): Whether you write your own regex or use a module, Perl supports both.

Common Pitfalls and Gotchas

  • Trying to parse Markdown with regex alone is error-prone for complex documents.
  • When using modules, ensure you handle the module's output correctly if inserting back into HTML pages (escaping may be needed).
  • Be mindful of different Markdown flavors (e.g., GFM, MultiMarkdown) requiring different parsers.

Summary

To convert Markdown to HTML in Perl with good reliability:

  • Use a well-established Perl module like Text::Markdown or Text::MultiMarkdown.
  • For simple cases or learning, a regex-based converter may suffice, but beware of limitations.
  • Understand that Perl’s powerful regex and string handling make this easy in principle, but Markdown’s complexity often demands dedicated parsers.

Verified Code

Executed in a sandbox to capture real output. • v5.34.1 • 10ms

Tip: edit code and use “Run (Browser)”. Server runs always execute the published, verified snippet.
STDOUT
<h1>Header 1</h1>

This is <em>emphasized</em> and this is <strong>strong</strong> text.

<h2>Header 2</h2>
STDERR
(empty)

Was this helpful?

Related Questions