Perl Dancer is a simple web application framework. It is so simple that you can start with just a single file.
The problem is when your application is growing. You usually add forms, models and model specific controllers. Perl dancer does not offer a best practice for structuring larger applications, but since this is perl it is fairly simple to structure your application. What I am presenting here is what has worked very well for me developing some larger dancer based applications. Your milleage may vary.