Each time the directive is processed, the referenced function (`preprocess`
in the example above) is called, and is passed named parameters. A "page"
parameter gives the name of the page that embedded the preprocessor
-directive, while a "destpage" parameter gices the name of the page the
+directive, while a "destpage" parameter gives the name of the page the
content is going to (different for inlined pages). All parameters included
in the directive are included as named parameters as well. Whatever the
function returns goes onto the page in place of the directive.