Simplified Common Lisp reference
Symbol class: Functions, Evaluation, Flow Control, Definitions and Syntax
Symbol type: special form
prognlist => value
Argument description:
list expressions

PROGN calls its expression in the order they have been written. Resulting value is the value of the last form unless non-local control flow forced earlier return. See also PROG1, PROG2.

Note that many macros and special forms behave partially as PROGN. It is called "implicit progn".

(progn 1 2 3 4 5) => 5
(progn 1 2 (sin 2.0) 4 (sin 1.0)) => 0.84147096
(progn) => NIL
Function indexFull documentation for progn (HyperSpec)