Embedding Perl in HTML with Mason

Chapter 2. Components

As mentioned in Chapter 1, the basic building block of Mason is called a component. A component consists of text of any sort as well as Mason-specific markup syntax. This chapter briefly introduces some core Mason concepts and then goes into the nitty-gritty of component syntax.

In this chapter we’ll introduce you to the syntax of Mason components, but we won’t spend much time on semantics. In most of the sections, we refer to other parts of the book where you can find out more about each concept.

Mason from 10,000 Feet

In order to put Mason into perspective, a basic understanding of how Mason processes a request is helpful. Each request is defined by an initial component path and a set of arguments to be passed to that component.

Requests are handled by the Interpreter object. You can use it directly or its API can be called by the ApacheHandler or CGIHandler modules provided with Mason.

The Interpreter asks the Resolver to fetch the requested component from the filesystem. Then the Interpreter asks the Compiler to create a “compiled” representation of the component. Mason’s compilation process consists of turning Mason source code into Perl code, which is then executed in order to create an object representing the component. Mason stores this generated Perl code on disk, so that it doesn’t need to go through the parsing and compilation process for every request, and stores the compiled code in an LRU (least recently used) cache in memory.

Once Mason has an object ...