That works. But so does changing the $app line to this–

From the docs–

The last statement of app.psgi should be a code reference that is a PSGI application:

The last statement isn't the sub declaration, it's the assignment. The variable name is meaningless. I personally prefer to just do an anonymous sub { … } as the last or only statement in this kind of test/one-off. But that’s only a style choice.