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.


package require Tcl 8.4 ; # throws an error if older
if {[info exists bloop] && [llength [info functions abs]]} {
    puts [expr abs($bloop)]
}