Task

 verify the version/revision of your currently running (compiler/interpreter/byte-compiler/runtime environment/whatever your language uses) and exit if it is too old.
 check whether the variable "bloop" exists and whether the math-function "abs()" is available and if yes compute abs(bloop).


Extra credit

 Report the number of integer variables in global scope, and their sum.


(let* ((ver (lisp-implementation-version))
       (major (parse-integer ver :start 0 :end (position #\. ver))))
  #+lispworks (assert (>= 5 major) () "Requires Lispworks version 5 or above")
  #+clisp (assert (>= 2 major) () "Requires CLISP 2.n")
  )