17.2.1.1 Examples of Satisfying a Two-Argument Test

 (remove "FOO" '(foo bar "FOO" "BAR" "foo" "bar") :test #'equal)
=>  (foo bar "BAR" "foo" "bar")
 (remove "FOO" '(foo bar "FOO" "BAR" "foo" "bar") :test #'equalp)
=>  (foo bar "BAR" "bar")
 (remove "FOO" '(foo bar "FOO" "BAR" "foo" "bar") :test #'string-equal)
=>  (bar "BAR" "bar")
 (remove "FOO" '(foo bar "FOO" "BAR" "foo" "bar") :test #'string=)
=>  (BAR "BAR" "foo" "bar")

 (remove 1 '(1 1.0 #C(1.0 0.0) 2 2.0 #C(2.0 0.0)) :test-not #'eql)
=>  (1)
 (remove 1 '(1 1.0 #C(1.0 0.0) 2 2.0 #C(2.0 0.0)) :test-not #'=)
=>  (1 1.0 #C(1.0 0.0))
 (remove 1 '(1 1.0 #C(1.0 0.0) 2 2.0 #C(2.0 0.0)) :test (complement #'=))
=>  (1 1.0 #C(1.0 0.0))

 (count 1 '((one 1) (uno 1) (two 2) (dos 2)) :key #'cadr) =>  2

 (count 2.0 '(1 2 3) :test #'eql :key #'float) =>  1

 (count "FOO" (list (make-pathname :name "FOO" :type "X")  
                    (make-pathname :name "FOO" :type "Y"))
        :key #'pathname-name
        :test #'equal)
=>  2