Mastering Perl
by  brian d foy

The unconfirmed error reports are from readers.  They have not yet been 
approved or disproved by the author or editor and represent solely the
opinion of the reader.

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

This page was updated April 8, 2008.


UNCONFIRMED  errors and comments from readers: 



[25] Lookarounds;
The regular expression that adds commas to numbers don't work.

$_ = '$1234.56789';
s/(?<!\.\d)(?<=\d)(?=(?:\d\d\d)+\b)/,/g;

will yield '$1,234.56,789'.


{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,:}.


(42) Fifth paragraph (second from end);
The inline code $arg[0] should be $args[0]


{44} second code example;
The code line reads:

setuid( $<, $< )

but should be

setuid( $< );


(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


(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.