MEMBER

(MEMBER <what> <list> [<test>])

If <what> is a member of <list> (in the sence of EQL), returns the rest
of the list starting with the matched element (just like in Common Lisp).
Othervise, returns false. If the <list> is dotted, the value after the
dot is silently ignored.

If the value of <test> is given, it must be a predicate of two arguments, 
first of them for <what>, and the second is for an item of the <list>; 
it will be used instead of EQL.

NOTE InteLib Lisp doesn't have key parameters so this version accepts 
the <test> argument as optional; it doesn't accept anything like CL's
MEMBER's :key or :test-not.