Mastering Perl
by  brian d foy

This errata page lists errors outstanding in the most recent printing.

If you have technical questions or error reports, you can send them to
booktech@oreilly.com.  Please specify the printing date of your copy.

This page was updated March 21, 2008.

Here's a key to the markup:
	[page-number]: serious technical mistake
	{page-number}: minor technical mistake
	<page-number>: important language/formatting problem
	(page-number): language change or minor formatting problem
	?page-number?: reader question or request for clarification



Confirmed errors:

(7) 2nd paragraph;
In fifth sentence, "firstF" should be "first".

{10} line 12;
That code should have the $i replaced with 0:

			print "\t\t\$&: ",
				substr( $_, $-[0], $+[0] - $-[0] ),
				"\n";


{13} 2nd paragraph;
My problem is precedence. The alternation is higher precedence than sequence,
Should be:
My problem is precedence. The alternation is lower precedence than sequence,


{19} code snippet continued from page 18;
The $type and $found variables are declared but never used.
Remove the line of code:
my( $type, $found );


(24) 2nd paragraph;
"The positive lookbehind assertion also looks backward, but its pattern must not match.
Should read "but its pattern must match."


{25} second code example on page;
The line:
$money =~ s/(?<=\d)(?=(?:\d\d\d)+$)/,/g; # $1,234.5,678

This is the code right after the line "but I still have that extra comma", and should read:

	$money = '$1234.5678';

	$money =~ s/(?<=\d)(?=(?:\d\d\d)+\b)/,/g;  # $1,234.5,678


[28] 2nd paragraph in section "Final Thoughts";
Replace the 2nd paragraph and following bit with:

I don't have to be content with the simple character classes such as
\w (word characters), \d (digits), and the others denoted
by slash sequences. I can also use the POSIX character classes. I
enclose those in the square brackets with colons on both sides of the
name, and then put them in a character class (so, two sets of square
braces):

	print "Found alphabetic character!\n" if  $string =~ m/[[:alpha:]]/;
	print "Found hex digit!\n"            if  $string =~ m/[[:xdigit:]]/;

I negate those with a caret, ^, after the first colon:

	print "Didn't find alphabetic characters!\n" if  $string =~ m/[[:^alpha:]]/;
	print "Didn't find spaces!\n" if  $string =~ m/[[:^space:]]/;



(31) 3rd paragraph of non-code text;
It appears a word is missing in the 4th sentence:

"... I've seen people do such as using ..."

should probably be

"... I've seen people do such things as using ..."


(36) Second code example under "Tainted Data" section;
Example reads:

$ perl tainted-args.pl
Argument [foo] is tainted

but it's missing the argument "foo". The example should read:

$ perl tainted-args.pl foo
Argument [foo] is tainted 


{95} First code example;
As written this example will produce very unexpected results. The line:

$diff = timediff( $t1, $t0 );
should be written:
$diff = timediff( $end, $start );


{119} First full sentence;
"Lower numbers are more severe, with 5 being the least severe:"
should be:
"Higher numbers are more severe, with 5 being the most severe problems:"


{129} Code in last section;
%dict = { 1 => 'one'};
should read
%dict = ( 1 => 'one' );


{139} code block;
The paragraph before the code example states: "I also label the loop REPL ..."
But the while loop has no label.
It should be:

My processing loop stays the same even if I add more operators. I also
label the loop REPL (for Read-Evaluate-Print), and I'll use that
label later when I want to control the looping from one of my
subroutines:

	#!/usr/bin/perl
	use strict;

	use vars qw( %Operators );
	%Operators = (
		'+'  => sub { $_[0] + $_[1] },
		'-'  => sub { $_[0] - $_[1] },
		'*'  => sub { $_[0] * $_[1] },
		'/'  => sub { $_[1] ? eval { $_[0] / $_[1] } : 'NaN' },
		);

	REPL: while( 1 )
		{
		my( $operator, @operand ) = get_line();

		my $some_sub = $Operators{ $operator };
		unless( defined $some_sub )
			{
			print "Unknown operator [$operator]\n";
			last REPL;
			}

		print $Operators{ $operator }->( @operand );
		}

	print "Done, exiting...\n";


	sub get_line
		{
		print "\nprompt> ";

		my $line = <STDIN>;

		$line =~ s/^\s+|\s+$//g;

		( split /\s+/, $line )[1,0,2];
		}


(182) Last sentence of first paragraph, first sentence of 2nd paragraph;
"If I give the switch the wrong sort of value, for instance, a string where I wanted a number, GetOptions doesn't set a value (so it doesn't turn a string into the number 0, for instance):

# code block

If I give the switch the wrong sort of value, for instance, a string where I wanted a number, GetOptions doesn't set a value."


I see a couple of issues here:
1) One sentence is repeated in both paragraphs ("If I give...a value.")
2) "for instance" is used twice in the first sentence.


{204} Last paragraph, first sentence;
Instead of:
In this short program I simply give die an anonymous array.
The sentence should be:
In this short program I simply give die an anonymous hash.



{215} Last line of root-logger.conf code;
	log4perl.appender.myFILE.layout.ConversionPattern = [%c] (%F line %L) %m%n
should be:
	log4perl.appender.myFILE.layout.ConversionPattern = [%p] (%F line %L) %m%n



{231} in sub show_arrays();
In the following subroutine

sub show_arrays {
foreach my $ref ( @_ ) {
>> print "Element [1,1] is $AoA->[1][1]\n";
}
}

print line should be:

>> print "Element [1,1] is $ref->[1][1]\n";


{270} top of page;
Remove this text at the end of that section. The PerlIO::scalar is the right module, but it loads XS stuff
so it's not right for talking about Perl-level tie stuff.

"You might already use tied variables without knowing it. In
Chapter 5 of T<Intermediate Perl>, we talked about opening a
filehandle to a scalar reference:

	open my($fh), ">", \$print_to_this_string
		or die "Could not open string: $!";

Once I have the filehandle, I do filehandle sorts of things with it.
How does it perform the magic? The M<IO::Scalar> module implements a
tied filehandle and takes responsibility for the filehandle behavior.
It can do whatever it likes, in this case printing to a scalar instead
of a file."


(274) 2nd full paragraph;
The second sentence of this paragraph says:

"... but with an the object form I can."
^^

Remove "an".

{275} Last paragraph;
Change the last paragraph on that page to:
From the output I can see that I start off with the value 1 in $number, but when I try to 
assign -5 (a value with a magnitude greater than 3), it doesn't work and the value is still 
1.  Normally my program would croak right there, but I used an eval to catch that error. 
The same thing happens for -4. When I try -3, it works:


(281) First paragraph under "Something a Bit More Realistic";
"... I have six possibilities." should read 
"... I have five possibilities."