** Using WeBWorK **

Does anyone know of a website or file I can look at to learn how to create sub-routines (or subclass, whichever it's called) to use in checking answers (I'd like to be able to offer hints and suggestions for students if it looks like they're going in some mistaken direction when answering a question).

Something that shows how to include some kind of custom sub-routine included within the Perl of a given question as well how to create a 'file'.pl file which can be used for many questions by simply loading 'file'.pl as a macro.

Thanks