How to make an HTTP GET request using LWP::UserAgent in Perl?

To make an HTTP GET request in Perl, LWP::UserAgent is one of the most popular core modules providing a clean, flexible interface for web interactions. It allows you to fetch URLs, handle headers, and get response content with ease.

Here is a step-by-step explanation with a runnable example to demonstrate how to perform a simple HTTP GET request using LWP::UserAgent:

Key Concepts:

• LWP::UserAgent is a high-level HTTP client.
• It creates a user-agent object to make requests
• HTTP responses are returned as HTTP::Response objects.
• You can check response success/failure with is_success, and get content with decoded_content.
• Perl sigils indicate variable types: $ for scalars (like objects), @ for arrays, and % for hashes.

Simple Working Example

use strict;
use warnings;
use LWP::UserAgent;

# Create a user agent object
my $ua = LWP::UserAgent->new;

# URL to fetch
my $url = 'http://www.example.com';

# Make the GET request
my $response = $ua->get($url);

# Check if the request was successful
if ($response->is_success) {
    print "Success! Response content:\n";
    # decoded_content handles character encoding correctly
    print $response->decoded_content;
} else {
    print "HTTP GET failed: ", $response->status_line, "\n";
}

Explanation

The example above performs these steps:

• Creates a LWP::UserAgent object called $ua.
• Defines a URL to fetch (http://www.example.com).
• Calls the get method on the user-agent object.
• The get method returns an HTTP::Response object stored in $response.
• It uses is_success to test for HTTP status 2xx.
• If successful, it prints the body of the response using decoded_content which respects content encoding (UTF-8, gzip, etc).
• If failed, it prints an error message with the HTTP code.

Common Pitfalls and Tips

• Always check is_success to avoid blindly trusting the response content.
• decoded_content is preferred over content to handle character encoding transparently.
• Timeouts and redirects can be configured via LWP::UserAgent attributes.
• Be careful with HTTPS URLs; LWP::UserAgent supports them but requires underlying SSL modules installed.
• Perl’s context: get returns a scalar HTTP::Response object.
• You can add headers by passing a second argument to get, e.g. $ua->get($url, 'Accept' => 'application/json').

Version Note

LWP::UserAgent is stable and available in Perl 5 distributions by default from very early versions. The usage remains consistent for Perl 5.6 and later. For HTTPS support, ensure that IO::Socket::SSL and related modules are installed.

This approach is a great starting point for basic HTTP requests in Perl. From here, you can explore POST requests, adding headers, cookies, and other features.