CL-USER> (defvar *foo* 42)
*FOO*
CL-USER> (let ((*foo* 24))
           (bar))
; in: LET ((*FOO* 24))
;     (BAR)
; 
; caught STYLE-WARNING:
;   undefined function: COMMON-LISP-USER::BAR
; 
; compilation unit finished
;   Undefined function:
;     BAR
;   caught 1 STYLE-WARNING condition

; No value
CL-USER> *foo*
24