[dancer-users] What can you do in the before hook? - Where is the documentation?

Hi, I was looking to set a catch-all route that will show "site is closed" and reached https://metacpan.org/pod/Dancer#hook specifically the hook before => sub { construct. It says what does the sub receive but it does not say what can one do with it. If the return value matters, etc. I am wondering if such documentation exists and if it would be a good idea to include it here or to link to it? Gabor