eturns 'pi if x is 3.14

(case* x ((#&lt;symbol?&gt;)))              ; returns #t if x is a symbol

(case* x (((+ 1 #&lt;symbol?&gt;))))        ; matches any list of the form '(+ 1 x) or any symbol in place of "x"

(case* x (((#&lt;symbol?&gt; #&lt;e1:...&gt; (+ #&lt;e2:...&gt;)))
          (append #&lt;e1&gt; #&lt;e2&gt;)))      ;  passed '(a b c d (+ 1 2)), returns '(b c d 1 2)

(case* x ((#&lt;"a.b"&gt;)))                ; matches if x is a string "a.b" where "." matches anything

(define (palindrome? x)