until ($isover) {
     clear_the_screen();
    print "Find the secret number between 1 and 100:  \n\n";
    LABEL:    print "Enter your guess: \n\n % "; #">" #in book's script; why?
    chomp($userguess = <STDIN>);

    #following "while" loop added by me in a "challenge"
    while ($userguess !~ /^[+-]?\d+$/ ) { #testing to see whether user entry is a number
       print "\nYour guess must be a number. Try again.  \n\n";
       goto LABEL;
    }