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.


when NimVersion < "1.2":
  error "This compiler is too old"                       # Error at compile time.
 
assert NimVersion >= "1.4", "This compiler is too old."  # Assertion defect at runtime.
 
var bloop = -12
 
when compiles abs(bloop):
  echo abs(bloop)