Chaining Input module (ChainMetaModule)

ChainMetaModule iterates through a set of modules until one returns a non-null value for the specified key. In this example, we chain together request-param, request-attr, session-attr and defaults modules. The 'skin' value is taken from the first that returns a non-null value, usually 'defaults'. Try adding '?skin=myskin' to the URL, and it should change.