Marc::lint is a perl module for checking the validity of marc records. most of the users will want to do something like is shown in the synopsis. other users may choose instead to overload marc::lint's methods and provide their own special field-level checking. if you have certain requirements, such as making sure that all 952 tags have a certain call number in them, you can write a function that checks for that, and still get all the benefits of the marc::lint framework.