-For preprocessor commands, the subroutine is passed named parameters. A
-"page" parameter gives the name of the page that embedded the preprocessor
-command. All parameters included in the preprocessor command are included
+ IkiWiki::hook(type => "preprocess", id => "foo", call => \&preprocess);
+
+Replace "foo" with the command name that will be used inside brackers for the preprocessor directive.
+
+Each time the directive is processed, the referenced subroutine (`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. All parameters included in the directive are included