Three global variables control the handling of exceptions in action list and action item operations.
The variable *handle-existing-action-list* controls the behavior of define-action-list when the action list already exists. It allows you to control independently both:
The variable *handle-existing-action-in-action-list* controls the behavior of define-action when the action already exists in the given action-list. It allows you to control independently both:
The variable *handle-missing-action-list* specifies behavior when one of undefine-action-list, print-actions, execute-actions, define-action and undefine-action is called on a missing action-list. By default, an error is signalled, but you can make it warn or ignore instead.
The variable *handle-missing-action-in-action-list* specifies behavior when you attempt to undefine a missing action. By default, a warning is signalled, but you can make it signal error, or ignore, instead.
LispWorks User Guide and Reference Manual - 21 Dec 2011