Embedding Perl in HTML with Mason

Chapter 10. Scalable Design

So now that you know how to do things with Mason, it’s time to start thinking about how to do things cleanly, scalably, and maintainably. Mason is a good tool, but it is not magic, and you still need to think about design when you use it.

Modules Versus Components

Mason is a powerful tool for generating content. Its combination of easy templating syntax, powerful component structures, and features like autohandlers, dhandlers, and component inheritance all combine to make it much like Perl itself: it makes easy things easy, and difficult things possible.

However, exactly like Perl itself, the facilities it provides can make it all too tempting to do things the easy way, and Mason makes no attempt to enforce any sort of discipline in your design. Instead, this is your responsibility as a programmer and application designer. This is where the responsibility always lies, no matter what language or tool you are using.

Though Mason is at its core a text templating tool, it also provides much more functionality. One such piece of functionality is that individual components are almost exactly like subroutines. They can be called anywhere in your processing and they can, in turn, call other components, generate output, and/or return values to the caller. And, like Perl’s subroutines, variables defined inside a component are lexically scoped to that component.

It is this similarity between components and subroutines that can lead to design trouble. As long-time ...