Another way not as compact but a little easier to read/follow. Would also handle if uscfollow wasn't 1 or 0 Tho i don't know when/if that would ever happen.
;; Toggle UCSFOLLOW using COND
(defun c:foo (/ v)
(setq v (getvar "UCSFOLLOW"))
(cond
((= v 1) ;; If it's currently ON turn it OFF
(setvar 'UCSFOLLOW 0)
(princ "\nUCSFOLLOW Desactivado")
)
((= v 0) ;; If it's currently OFF turn it ON
(setvar "UCSFOLLOW" 1)
(princ "\nUCSFOLLOW Activado")
)
(T ;; If it’s some unexpected value, default to OFF
(setvar "UCSFOLLOW" 0)
(princ "\nUCSFOLLOW Desactivado")
)
)
(princ)
)