Here's a list I have compiled of corrections to the codes and text in the
"Teach Yourself PERL in 21 Days":

The title is incorrect, the book should be titled "Teach yourself PERL
in 21 Weeks."  ;-)

CHAPTER 4:

-Listing 4.1
line 7          $exponent = <INPUT>;
should read     $exponent = <STDIN>;

CHAPTER 5:

-Listing 5.8
line 5          @subarray = @array(@range);
should read     @subarray = @array[@range];

CHAPTER 8:
-Listing 8.11
        $total is 10, not 9 if you use his input.

        The error is on line 6 of Listing 8.11. Notice that the pattern to
        match in the substitution is: "one or more tabs or spaces followed by a
        single newline at the end of the line".In reality he wants ZERO or
        more tabs or spaces followed by a newline at the end of the line, in
        order to have the pattern match *every* time and therefore get rid of
        the newline every time.
        OR
        he could have put the '\n' inside of the [] so the pattern
        would match every time and remove the newline every time.

So the fix is:

line 6          $line =~ s/{/t ]+n$//;
should read     $line =~ s/[\t ]*\n$//;  #first option
OR
                $line =~ s/[\t \n]+$//;  #second option

-Listing 8.13
        same problem as 8.11. Correct line 8.

line 9          if (line ne "") {
should read     if ($line ne "") {

line 15         };
        This is fine. the semi-colin, when not needed is ignored. The
line could read };;;;;;; and would still work.

CHAPTER 9:
-Listing 9.10
line 7,8,9
        The order of these is messed up. The correct order is either:
        9,8,7 OR 8,7,9. The extraneous whitespace _must_ be removed before
        doing the character count.

-Listing 9.11
line 20,21,22
        Same thing as listing 9.10. Make it 22,21,20 OR 21,20,22.

line 23         last if ($linecount == 3);
should read     last if ($linecount == $numline);
        The variable $numline is set, but never used if you don't change
        this line.


That's it so far. I didn't find any errors through Chapter 12. After
that, I only used the book for reference.

I have the listings (programs) in the book (and a few others) at:
http://oz.uc.edu/~solkode/.scripts/
(I don't know if they contain the fixes, and a couple _do_ have typos and
don't work (R1.1 and 10.1 come to mind)).

Thanks to Robert C. Knauer<rcktexas@ix.netcom.com> for some of the
solutions. If you find any others, please let me know.