Well, if you look at line 57:

    55  while ( my ($punctuation, $count) = each(%wordHash) )
    56  {    
    57      $wordArray[my $i] = "$count\t$punctuation";
    58      $i++;
    59      print ("$count\t$charnames{$punctuation}\n");
    60  }
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You'll see that in line 57 you declare a variable inside the square brackets of an array access. Each time through the loop you'll get a new $i which, since you haven't initialized it, will have an undefined value. What you probably want is to just push the next value onto @wordArray instead.