- (cond ((null variable)
- (error "Nihil ex nihil, NIL can't be set."))
- ((eq variable t)
- (error "Veritas aeterna, T can't be set."))
- ((and (boundp '*keyword-package*)
- (keywordp variable))
- (error "Keywords can't be set."))
- (t
- (%set-symbol-value variable new-value))))