A doctype comes with a set of usual modules to use. Without having to mucking about with the doctypes, you can quickly activate or disable these modules by specifying which modules you wish to allow with this directive. This is most useful for unit testing specific modules, although end users may find it useful for their own ends.
If you specify a module that does not exist, the manager will silently fail to use it, so be careful! User-defined modules are not affected by this directive. Modules defined in %HTML.CoreModules are not affected by this directive.
--# vim: et sw=4 sts=4