Modperl

Mod_perl is an Apache module that embeds a Perl interpreter inside the web server, allowing Perl code to handle HTTP requests with direct access to Apache internals. By keeping the interpreter loaded across requests, mod_perl can execute Perl scripts more efficiently than starting a new interpreter for each request.

Two major variants exist. mod_perl 1.x integrates with Apache 1.x, while mod_perl 2.x is a complete rewrite for Apache 2.x and relies on the Apache Portable Runtime and API 2. It provides Perl handlers, filters, and content generation that can access Apache request, connection, and server objects, enabling deep customization of the request lifecycle.

Applications can benefit from persistent state and reduced startup overhead, making mod_perl well suited for high-traffic Perl web applications. It also offers broad access to CPAN modules and server-side data, which can simplify complex logic. However, embedding an interpreter in the server increases memory usage and adds complexity.

Careful attention to thread safety, module compatibility, and resource management is required, especially when using threaded MPMs in Apache 2.x. Mod_perl remains a mature option in many deployments, though newer deployment models such as PSGI/Plack are increasingly popular for Perl web development.