While Mojolicious contains a really nice built in web server, which makes especially development and testing very enjoyable, we also have first class support for PSGI and Plack.

In fact, it easily beats most web frameworks that were specifically designed for Plack from the get-go.
All Mojolicious applications can automatically detect that they are executed in a PSGI context and act accordingly.

Isn't it pretty?
Everything, including middleware, just works out of the box! :)