Mastering Perl

Errata for Mastering Perl

Submit your own errata for this product.


The errata list is a list of errors and their corrections that were found after the product was released. If the error was corrected in a later version or reprint the date of the correction will be displayed in the column titled "Date Corrected".

The following errata were submitted by our customers and approved as valid errors by the author or editor.

Color Key: Serious Technical Mistake Minor Technical Mistake Language or formatting error Typo Question Note Update



Version Location Description Submitted By Date Submitted Date Corrected
PDF
Page 10
1st bunch of code

my $regex = eval { qr/$pattern/ }; die "Check your pattern! $@" if $@; while( <> ) { if( m/$regex/ ) { print "$_"; print "\t\t\$&: ", substr( $_, $-[$i], $+[$i] - $-[$i] ), ## Error "\n"; foreach my $i ( 1 .. $#- ) { print "\t\t\$$i: ", substr( $_, $-[$i], $+[$i] - $-[$i] ), "\n"; } } } ## The first substr line is invalid. $i is not even initialized.

Note from the Author or Editor:
Change that line to substr( $_, $-[0], $+[0] - $-[0] ),

Anonymous  Jan 04, 2011 
PDF
Page 24
2nd paragraph

"The positive lookbehind assertion also looks backward, but its pattern must not match." It should match

Note from the Author or Editor:
Change as noted

Anonymous  Jan 04, 2011 
Printed
Page 25
Lookarounds

The regular expression that adds commas to numbers don't work. $_ = '$1234.56789'; s/(?<!.d)(?<=d)(?=(?:ddd)+)/,/g; will yield '$1,234.56,789'.

Note from the Author or Editor:
The example is just wrong and there's not a pleasing way to fix it.

Anonymous   
Printed
Page 28
Final Thoughts

m/[:alpha:]/ should be m/[[:alpha:]]/, and so on. Otherwise, m/[:alpha:]/ matches a character from the class {:,a,l,p,h,a,:}.

Note from the Author or Editor:
Change as noted

Anonymous   
Safari Books Online
30
first examples of section "final thoughts"

Examples such as: print "Didn't find spaces!\n" if $string =~ m/[:^space:]/; don't do what the text suggests. Not finding spaces is not the same as finding non-spaces. There are four occurences of this (two with [:^, two with \P).

Note from the Author or Editor:
Those lines should read: I negate those with a caret, C<^>, after the first colon: print "Found non-alphabetics!\n" if $string =~ m/[[:^alpha:]]/; print "Found non-spaces!\n" if $string =~ m/[[:^space:]]/; I can say the same thing in another way by specifying a named property. The C<\p{Name}> sequence (little p) includes the characters for the named property, and the C<\P{Name}> sequence (big P} is its complement: print "Found ASCII character!\n" if $string =~ m/\p{IsASCII}/; print "Found control characters!\n" if $string =~ m/\p{IsCntrl}/; print "Found non-punctuation characters!\n" if $string =~ m/\P{IsPunct}/; print "Found non-uppercase characters!\n" if $string =~ m/\P{IsUpper}/;

Manuel Pégourié-Gonnard  Aug 27, 2010 
PDF
Page 36
Tainted Data

$ perl tainted-args.pl Argument [foo] is tainted ## Should be $ perl -T tainted-args.pl foo

Note from the Author or Editor:
Change as noted

Anonymous  Jan 04, 2011 
Printed
Page 42
Fifth paragraph (second from end)

The inline code $arg[0] should be $args[0]

Note from the Author or Editor:
Change as noted

Anonymous   
Printed
Page 44
second code example

The code line reads: setuid( $<, $< ) but should be setuid( $< );

Note from the Author or Editor:
Change as noted.

Anonymous   
Printed
Page 48
second to last code example

The code line reads: The value of var before is [$var] at program.pl line 123 That is sample output and the double string interpolation will have filled in $var with its value. Since I don't give $var a value in the example, note that with three dots: The value of var before is [...] at program.pl line 123

Note from the Author or Editor:
Change as noted

Anonymous   
Printed
Page 131
Missing text before section "Typeglobs"

The section "The Symbol Table", in a nutshell, explains how the set of package variables can be accessed in a hash-like fashion, and features an example showing the strong association between the two: creating variables causes them to appear in the hash-like structure. The last step of the example (starting middle of page 130) shows "I can delete all the variables with the same name", using the delete operator. The output of the example does indeed show that the result is the removal of the variables *n and *m from the symbol table for package Foo, but it also shows that the variables themselves are not gone -- $n and $m still have their previous values. I was expecting that the variables themselves would cease to exist. The example output is _correct_ in that the variables are gone from the symbol table yet still exist when referenced by name, so maybe my expectations are just wrong. But... Since the section is showing the correlation between variables and the symbol table, ending it with no explanation of the discrepancy illustrated by the final example left me hanging and confused. An extra paragraph would be helpful here.

Note from the Author or Editor:
Variables are just names that we use in source code to refer to values. Although a variable name might disappear at runtime, the values don't necessarily disappear. Once Perl know which value it's using, the name doesn't matter.

Anonymous   
Printed
Page 320
Index: Perl Best Practices

Perl Best Practices is also mentioned on page 118.

Note from the Author or Editor:
Update index entry for Perl Best Practices to include page 118

Anonymous  Nov 20, 2008