Make the UTF-8 decoding stricter and more verbose when

[p5sagit/p5-mst-13.2.git] / pod / perlre.pod

diff --git a/pod/perlre.pod b/pod/perlre.pod
index e1f30a3..380bc5f 100644 (file)
--- a/pod/perlre.pod
+++ b/pod/perlre.pod
@@ -169,7 +169,7 @@ You'll need to write something like C<m/\Quser\E\@\Qhost/>.
 In addition, Perl defines the following:
 
     \w Match a "word" character (alphanumeric plus "_")
-    \W Match a non-word character
+    \W Match a non-"word" character
     \s Match a whitespace character
     \S Match a non-whitespace character
     \d Match a digit character
@@ -180,7 +180,7 @@ In addition, Perl defines the following:
         equivalent to C<(?:\PM\pM*)>
     \C Match a single C char (octet) even under utf8.
 
-A C<\w> matches a single alphanumeric character, not a whole word.
+A C<\w> matches a single alphanumeric character or C<_>, not a whole word.
 Use C<\w+> to match a string of Perl-identifier characters (which isn't 
 the same as matching an English word).  If C<use locale> is in effect, the
 list of alphabetic characters generated by C<\w> is taken from the
@@ -199,24 +199,30 @@ equivalents (if available) are as follows:
     alpha
     alnum
     ascii
+    blank              [1]
     cntrl
     digit       \d
     graph
     lower
     print
     punct
-    space       \s
+    space       \s     [2]
     upper
-    word        \w
+    word        \w     [3]
     xdigit
 
+  [1] A GNU extension equivalent to C<[ \t]>, `all horizontal whitespace'.
+  [2] Not I<exactly equivalent> to C<\s> since the C<[[:space:]]> includes
+      also the (very rare) `vertical tabulator', "\ck", chr(11).
+  [3] A Perl extension. 
+
 For example use C<[:upper:]> to match all the uppercase characters.
-Note that the C<[]> are part of the C<[::]> construct, not part of the whole
-character class.  For example:
+Note that the C<[]> are part of the C<[::]> construct, not part of the
+whole character class.  For example:
 
     [01[:alpha:]%]
 
-matches one, zero, any alphabetic character, and the percentage sign.
+matches zero, one, any alphabetic character, and the percentage sign.
 
 If the C<utf8> pragma is used, the following equivalences to Unicode
 \p{} constructs hold:
@@ -224,6 +230,7 @@ If the C<utf8> pragma is used, the following equivalences to Unicode
     alpha       IsAlpha
     alnum       IsAlnum
     ascii       IsASCII
+    blank      IsSpace
     cntrl       IsCntrl
     digit       IsDigit
     graph       IsGraph
@@ -238,8 +245,8 @@ If the C<utf8> pragma is used, the following equivalences to Unicode
 For example C<[:lower:]> and C<\p{IsLower}> are equivalent.
 
 If the C<utf8> pragma is not used but the C<locale> pragma is, the
-classes correlate with the isalpha(3) interface (except for `word',
-which is a Perl extension, mirroring C<\w>).
+classes correlate with the usual isalpha(3) interface (except for
+`word' and `blank').
 
 The assumedly non-obviously named classes are:
 
@@ -250,23 +257,24 @@ The assumedly non-obviously named classes are:
 Any control character.  Usually characters that don't produce output as
 such but instead control the terminal somehow: for example newline and
 backspace are control characters.  All characters with ord() less than
-32 are most often classified as control characters.
+32 are most often classified as control characters (assuming ASCII,
+the ISO Latin character sets, and Unicode).
 
 =item graph
 
-Any alphanumeric or punctuation character.
+Any alphanumeric or punctuation (special) character.
 
 =item print
 
-Any alphanumeric or punctuation character or space.
+Any alphanumeric or punctuation (special) character or space.
 
 =item punct
 
-Any punctuation character.
+Any punctuation (special) character.
 
 =item xdigit
 
-Any hexadecimal digit.  Though this may feel silly (/0-9a-f/i would
+Any hexadecimal digit.  Though this may feel silly ([0-9A-Fa-f] would
 work just fine) it is included for completeness.
 
 =back
@@ -352,7 +360,7 @@ everything before the matched string.  And C<$'> returns everything
 after the matched string.
 
 The numbered variables ($1, $2, $3, etc.) and the related punctuation
-set (C<<$+>, C<$&>, C<$`>, and C<$'>) are all dynamically scoped
+set (C<$+>, C<$&>, C<$`>, and C<$'>) are all dynamically scoped
 until the end of the enclosing block or until the next successful
 match, whichever comes first.  (See L<perlsyn/"Compound Statements">.)
 
@@ -377,10 +385,11 @@ that looks like \\, \(, \), \<, \>, \{, or \} is always
 interpreted as a literal character, not a metacharacter.  This was
 once used in a common idiom to disable or quote the special meanings
 of regular expression metacharacters in a string that you want to
-use for a pattern. Simply quote all non-alphanumeric characters:
+use for a pattern. Simply quote all non-"word" characters:
 
     $pattern =~ s/(\W)/\\$1/g;
 
+(If C<use locale> is set, then this depends on the current locale.)
 Today it is more common to use the quotemeta() function or the C<\Q>
 metaquoting escape sequence to disable all metacharacters' special
 meanings like this:
@@ -673,7 +682,7 @@ The "grab all you can, and do not give anything back" semantic is desirable
 in many situations where on the first sight a simple C<()*> looks like
 the correct solution.  Suppose we parse text with comments being delimited
 by C<#> followed by some optional (horizontal) whitespace.  Contrary to
-its appearence, C<#[ \t]*> I<is not> the correct subexpression to match
+its appearance, C<#[ \t]*> I<is not> the correct subexpression to match
 the comment delimiter, because it may "give up" some whitespace if
 the remainder of the pattern can be made to match that way.  The correct
 answer is either one of these: