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.


if not? sys\version > 0.9.0 -> panic "version too old!"
 
bloop: 3 - 5
 
if? set? 'bloop -> "variable 'bloop' is set"
else            -> "variable 'bloop' is not set"
 
if set? 'abs -> print ["the absolute value of bloop is:" abs bloop]
 
print [
    "The sum of all globally defined integers is:"
    sum map select keys symbols 'sym -> integer? var sym
                                'sym -> var sym
]