The joy of PSGI middleware
I must admit that I rarely feel comfortable with (web application) frameworks - each system facilitates a certain type of task but it complicates the missing parts. Good frameworks support extension via plugins, but each framework has its own plugin architecture to learn. That's why I like PSGI so much - it only specifies how to connect things. This is how PSGI looks like to me (image CC-BY-SA by CMG Lee):