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Introduced in September 2009 by Tatsuhiko Miyagawa, PSGI is already on its way to becoming the preferred paradigm for Perl web programming.
PSGI is an interface between Perl web applications and web servers, inspired by Python's WSGI and Ruby's Rack. Plack is a module and a collection of utilities and middleware which facilitates creating and running web applications conforming to that interface. Together, they have the potential to transform the landscape of Perl web programming by reducing duplication of effort and dramatically increasing flexibility and ease of deployment.
After a general overview of PSGI and the problems it is intended to solve, we will see a few examples of the wonderful things that can already be accomplished with Plack and related modules and tools, and the benefits it offers relative to more established contenders, especially mod_perl.