lispdoc - results for unless

(unless test &body forms)
Function: If the first argument is not true, the rest of the forms are evaluated as a PROGN.
Example:
(defun file-pathname-p (p)
  (unless (directory-pathname-p p) p))
Mentioned in:
CLtL2 - 24.1. General Error-Signaling Functions
CLtL2 - 26.10. Conditional Execution
CLtL2 - 26.3.2. Kinds of Loop Clauses
CLtL2 - 6. Predicates
CLtL2 - 6.4. Logical Operators
CLtL2 - 7. Control Structure
CLtL2 - 7.10.2. Rules Governing the Passing of Multiple Values
CLtL2 - 7.6. Conditionals
HyperSpec - Macro WHEN, UNLESS
On Lisp - Adding Prolog Features
On Lisp - Chapter _28
On Lisp - New Utilities (Computation at Compile-Time)
On Lisp - Objects in Plain Lisp
On Lisp - Referential Transparency
PCL - and or and not
PCL - the mighty loop
PCL - when and unless