lispdoc - results for pushnew

(pushnew obj place &rest keys &key key test test-not &environment env)
Function: Takes an object and a location holding a list. If the object is already in the list, does nothing; otherwise, conses the object onto the list. Returns the modified list. If there is a :TEST keyword, this is used for the comparison.
Example:
(defun add-spres-flag! (flag)
  (pushnew flag *spres-flags*))
Mentioned in:
CLtL2 - 15.2. Lists
CLtL2 - 15.5. Using Lists as Sets
CLtL2 - 7.2. Generalized Variables
HyperSpec - Macro PUSHNEW
PCL - other ways to modify places
PCL - sets