UNWIND-PROTECT
==============

syntax: (unwind-protect <protected-form> 
                        {<cleanup-form> ...})

Sometimes it is necessary to evaluate a form and to 
secure that certain side effects take place later. 
When the program stops (in a normal or not normal 
way), then the cleanup-form will be executed.

example:       >(unwind-protect
                       (progn (start-motor)
                              (drill-hole))
                       (stop-motor))