delete command weirdness

Anyone have an explanation for the inability of the delete command to
delete the car from a list (at least in clisp)? I guess this falls
under the category of "never expect destructive list functions to act
how you expect."


CL-USER> (defvar testing)
TESTING
CL-USER> (setq testing '(a b c d))
(A B C D)
CL-USER> (delete 'a testing)
(B C D)
CL-USER> testing
(A B C D)
CL-USER> (delete 'b testing)
(A C D)
CL-USER> testing
(A C D)


-Nat