You are suffering from premature incrementation :)

And, for goodness' sake, use warnings;. This would have shown you that you incremented past the end of your @correct array (the first index of an array in perl is 0, not 1). I added these print statements to show the problem:

    print "guess=$guess=\n";
    print "correct[$i]=$correct[$i]=\n";
     if ($guess eq $correct[$i]) { # if guess is correct, reply
        print "You Rock!\n";
        $i++;
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