Simplified Common Lisp reference
Symbol class: Functions, Evaluation, Flow Control, Definitions and Syntax
Symbol type: macro
caseexpressionvariants(zero or more) => an object
Argument description:
expression a value used to distinguish between variants
variants list of match-values and code variants

CASE macro is used for branching. Variants are tested sequentially for EQL equality with from the top. See also IF, CASE.

(case (+ 1 2)
      (5 "variant 1, five")
      ((2 3) "variant 2, two or three")
      (otherwise "variant 3, none of above")) => "variant 2, two or three"
Function indexFull documentation for case (HyperSpec)