🐫 JSON with Perl – Encode, Decode, and Exchange Data (2025 Guide)

🧲 Introduction – Why Use JSON in Perl?

Perl, known for its powerful text processing capabilities, supports JSON seamlessly through core modules like JSON, JSON::XS, and Cpanel::JSON::XS. These modules allow developers to encode Perl data structures into JSON and decode JSON into Perl hashes and arrays, making it ideal for building REST APIs, web services, and automation scripts.

🎯 In this guide, you’ll learn:

• How to encode and decode JSON in Perl
• Core modules and syntax
• Real-world examples for APIs and file handling
• Best practices for clean and efficient code

📦 Step 1: Load JSON Module in Perl

Install via CPAN if not already available:

cpan JSON

Or include it in your script:

use JSON;

✅ Encoding Perl Data to JSON

🧪 Example – Convert Hash to JSON String

use JSON;

my %user = (
  name  => "Alice",
  age   => 30,
  email => "alice@example.com"
);

my $json_text = encode_json(\%user);
print "$json_text\n";

🔍 Output:

{"name":"Alice","age":30,"email":"alice@example.com"}

✔️ encode_json() takes a reference to a hash or array and returns a JSON string.

🔁 Decoding JSON to Perl Data

🧪 Example – JSON String to Hash

use JSON;

my $json_string = '{"name":"Bob","age":25}';
my $perl_hash = decode_json($json_string);

print "Name: $perl_hash->{name}\n";  # Output: Bob

✔️ decode_json() turns JSON into a Perl reference (hashref or arrayref).

📡 Reading JSON from a File

🧪 Example – Load and Decode JSON File

use JSON;
use strict;
use warnings;

open my $fh, '<', 'data.json' or die "Can't open file: $!";
local $/;  # Slurp mode
my $json_text = <$fh>;
close $fh;

my $data = decode_json($json_text);
print "User: $data->{name}\n";

🚀 Sending JSON in a Perl API (PSGI/Plack)

use Plack::Request;
use JSON;

my $app = sub {
  my $req = Plack::Request->new(shift);
  
  my %data = (
    message => "Hello from Perl API",
    status  => "ok"
  );
  
  my $res = $req->new_response(200);
  $res->content_type('application/json');
  $res->body(encode_json(\%data));
  return $res->finalize;
};

✔️ Sends a JSON response from a Perl-based API service.

🧠 Common JSON Modules in Perl

🛡️ Best Practices for JSON in Perl

📌 Summary – Recap & Next Steps

JSON with Perl is straightforward and powerful, especially when building CLI tools, RESTful APIs, or server-side scripts that require reliable data exchange.

🔍 Key Takeaways:

• Use encode_json() and decode_json() for conversion
• JSON data in Perl is represented as references
• Supports API responses, config files, and data logs
• Perl modules like JSON::XS offer performance benefits

⚙️ Real-world use:

Used in API development, data processing scripts, config management, and web backend services.

❓ FAQ – JSON in Perl

❓ Which JSON module should I use in Perl?
✅ Use JSON::XS or Cpanel::JSON::XS for performance; JSON for portability.

❓ How do I convert a Perl array to JSON?
✅ Use encode_json(\@array) to get a JSON array string.

❓ What does decode_json() return?
✅ A reference to a hash or array, depending on the JSON structure.

❓ Can I use JSON in CGI Perl scripts?
✅ Yes. Just set the content type to application/json and use encode_json().