Update IO-Compress to CPAN version 2.040

[perl5.git] / pod / perlreref.pod

diff --git a/pod/perlreref.pod b/pod/perlreref.pod
index 5ce6463..11da56d 100644 (file)
--- a/pod/perlreref.pod
+++ b/pod/perlreref.pod
@@ -10,63 +10,80 @@ as the L</"SEE ALSO"> section in this document.
 
 =head2 OPERATORS
 
 
 =head2 OPERATORS
 

-  =~ determines to which variable the regex is applied.
-     In its absence, $_ is used.
-
-        $var =~ /foo/;
-
-  !~ determines to which variable the regex is applied,
-     and negates the result of the match; it returns
-     false if the match succeeds, and true if it fails.
-
-       $var !~ /foo/;
-
-  m/pattern/igmsoxc searches a string for a pattern match,
-     applying the given options.
-
-        i  case-Insensitive
-        g  Global - all occurrences
-        m  Multiline mode - ^ and $ match internal lines
-        s  match as a Single line - . matches \n
-        o  compile pattern Once
-        x  eXtended legibility - free whitespace and comments
-        c  don't reset pos on failed matches when using /g
-
-     If 'pattern' is an empty string, the last I<successfully> matched
-     regex is used. Delimiters other than '/' may be used for both this
-     operator and the following ones.
-
-  qr/pattern/imsox lets you store a regex in a variable,
-     or pass one around. Modifiers as for m// and are stored
-     within the regex.
-
-  s/pattern/replacement/igmsoxe substitutes matches of
-     'pattern' with 'replacement'. Modifiers as for m//
-     with one addition:
-
-        e  Evaluate replacement as an expression
-
-     'e' may be specified multiple times. 'replacement' is interpreted
-     as a double quoted string unless a single-quote (') is the delimiter.
-
-  ?pattern? is like m/pattern/ but matches only once. No alternate
-      delimiters can be used. Must be reset with L<reset|perlfunc/reset>.
+C<=~> determines to which variable the regex is applied.
+In its absence, $_ is used.
+
+    $var =~ /foo/;
+
+C<!~> determines to which variable the regex is applied,
+and negates the result of the match; it returns
+false if the match succeeds, and true if it fails.
+
+    $var !~ /foo/;
+
+C<m/pattern/msixpogcdual> searches a string for a pattern match,
+applying the given options.
+
+    m  Multiline mode - ^ and $ match internal lines
+    s  match as a Single line - . matches \n
+    i  case-Insensitive
+    x  eXtended legibility - free whitespace and comments
+    p  Preserve a copy of the matched string -
+       ${^PREMATCH}, ${^MATCH}, ${^POSTMATCH} will be defined.
+    o  compile pattern Once
+    g  Global - all occurrences
+    c  don't reset pos on failed matches when using /g
+    a  restrict \d, \s, \w and [:posix:] to match ASCII only
+    aa (two a's) also /i matches exclude ASCII/non-ASCII
+    l  match according to current locale
+    u  match according to Unicode rules
+    d  match according to native rules unless something indicates
+       Unicode
+
+If 'pattern' is an empty string, the last I<successfully> matched
+regex is used. Delimiters other than '/' may be used for both this
+operator and the following ones. The leading C<m> can be omitted
+if the delimiter is '/'.
+
+C<qr/pattern/msixpodual> lets you store a regex in a variable,
+or pass one around. Modifiers as for C<m//>, and are stored
+within the regex.
+
+C<s/pattern/replacement/msixpogcedual> substitutes matches of
+'pattern' with 'replacement'. Modifiers as for C<m//>,
+with two additions:
+
+    e  Evaluate 'replacement' as an expression
+    r  Return substitution and leave the original string untouched.
+
+'e' may be specified multiple times. 'replacement' is interpreted
+as a double quoted string unless a single-quote (C<'>) is the delimiter.
+
+C<?pattern?> is like C<m/pattern/> but matches only once. No alternate
+delimiters can be used.  Must be reset with reset().

 
 =head2 SYNTAX
 
 
 =head2 SYNTAX
 

-   \       Escapes the character immediately following it
-   .       Matches any single character except a newline (unless /s is used)
-   ^       Matches at the beginning of the string (or line, if /m is used)
-   $       Matches at the end of the string (or line, if /m is used)
-   *       Matches the preceding element 0 or more times
-   +       Matches the preceding element 1 or more times
-   ?       Matches the preceding element 0 or 1 times
-   {...}   Specifies a range of occurrences for the element preceding it
-   [...]   Matches any one of the characters contained within the brackets
-   (...)   Groups subexpressions for capturing to $1, $2...
-   (?:...) Groups subexpressions without capturing (cluster)
-   |       Matches either the subexpression preceding or following it
-   \1, \2 ...  The text from the Nth group
+ \       Escapes the character immediately following it
+ .       Matches any single character except a newline (unless /s is
+           used)
+ ^       Matches at the beginning of the string (or line, if /m is used)
+ $       Matches at the end of the string (or line, if /m is used)
+ *       Matches the preceding element 0 or more times
+ +       Matches the preceding element 1 or more times
+ ?       Matches the preceding element 0 or 1 times
+ {...}   Specifies a range of occurrences for the element preceding it
+ [...]   Matches any one of the characters contained within the brackets
+ (...)   Groups subexpressions for capturing to $1, $2...
+ (?:...) Groups subexpressions without capturing (cluster)
+ |       Matches either the subexpression preceding or following it
+ \g1 or \g{1}, \g2 ...    Matches the text from the Nth group
+ \1, \2, \3 ...           Matches the text from the Nth group
+ \g-1 or \g{-1}, \g-2 ... Matches the text from the Nth previous group
+ \g{name}     Named backreference
+ \k<name>     Named backreference
+ \k'name'     Named backreference
+ (?P=name)    Named backreference (python syntax)

 
 =head2 ESCAPE SEQUENCES
 
 
 =head2 ESCAPE SEQUENCES
 


@@ -78,18 +95,20 @@ These work as in normal strings.
    \n       Newline
    \r       Carriage return
    \t       Tab
    \n       Newline
    \r       Carriage return
    \t       Tab

-   \038     Any octal ASCII value
-   \x7f     Any hexadecimal ASCII value
-   \x{263a} A wide hexadecimal value
+   \037     Char whose ordinal is the 3 octal digits, max \777
+   \o{2307} Char whose ordinal is the octal number, unrestricted
+   \x7f     Char whose ordinal is the 2 hex digits, max \xFF
+   \x{263a} Char whose ordinal is the hex number, unrestricted

    \cx      Control-x
    \cx      Control-x

-   \N{name} A named character
+   \N{name} A named Unicode character or character sequence
+   \N{U+263D} A Unicode character by hex ordinal

 
    \l  Lowercase next character
    \u  Titlecase next character
    \L  Lowercase until \E
    \U  Uppercase until \E
    \Q  Disable pattern metacharacters until \E
 
    \l  Lowercase next character
    \u  Titlecase next character
    \L  Lowercase until \E
    \U  Uppercase until \E
    \Q  Disable pattern metacharacters until \E

-   \E  End case modification
+   \E  End modification

 
 For Titlecase, see L</Titlecase>.
 
 
 For Titlecase, see L</Titlecase>.
 


@@ -104,44 +123,74 @@ This one works differently from normal strings:
    [f-j-]   Dash escaped or at start or end means 'dash'
    [^f-j]   Caret indicates "match any character _except_ these"
 
    [f-j-]   Dash escaped or at start or end means 'dash'
    [^f-j]   Caret indicates "match any character _except_ these"
 

-The following work within or without a character class:
-
-   \d      A digit, same as [0-9]
-   \D      A nondigit, same as [^0-9]
-   \w      A word character (alphanumeric), same as [a-zA-Z0-9_]
-   \W      A non-word character, [^a-zA-Z0-9_]
-   \s      A whitespace character, same as [ \t\n\r\f]
-   \S      A non-whitespace character, [^ \t\n\r\f]
-   \C      Match a byte (with Unicode, '.' matches char)
+The following sequences (except C<\N>) work within or without a character class.
+The first six are locale aware, all are Unicode aware. See L<perllocale>
+and L<perlunicode> for details.
+
+   \d      A digit
+   \D      A nondigit
+   \w      A word character
+   \W      A non-word character
+   \s      A whitespace character
+   \S      A non-whitespace character
+   \h      An horizontal whitespace
+   \H      A non horizontal whitespace
+   \N      A non newline (when not followed by '{NAME}'; experimental;
+           not valid in a character class; equivalent to [^\n]; it's
+           like '.' without /s modifier)
+   \v      A vertical whitespace
+   \V      A non vertical whitespace
+   \R      A generic newline           (?>\v|\x0D\x0A)
+
+   \C      Match a byte (with Unicode, '.' matches a character)

    \pP     Match P-named (Unicode) property
    \pP     Match P-named (Unicode) property

-   \p{...} Match Unicode property with long name
+   \p{...} Match Unicode property with name longer than 1 character

    \PP     Match non-P
    \PP     Match non-P

-   \P{...} Match lack of Unicode property with long name
-   \X      Match extended unicode sequence
+   \P{...} Match lack of Unicode property with name longer than 1 char
+   \X      Match Unicode extended grapheme cluster

 
 POSIX character classes and their Unicode and Perl equivalents:
 
 
 POSIX character classes and their Unicode and Perl equivalents:
 

-   alnum   IsAlnum             Alphanumeric
-   alpha   IsAlpha             Alphabetic
-   ascii   IsASCII             Any ASCII char
-   blank   IsSpace  [ \t]      Horizontal whitespace (GNU)
-   cntrl   IsCntrl             Control characters
-   digit   IsDigit  \d         Digits
-   graph   IsGraph             Alphanumeric and punctuation
-   lower   IsLower             Lowercase chars (locale aware)
-   print   IsPrint             Alphanumeric, punct, and space
-   punct   IsPunct             Punctuation
-   space   IsSpace  [\s\ck]    Whitespace
-           IsSpacePerl   \s    Perl's whitespace definition
-   upper   IsUpper             Uppercase chars (locale aware)
-   word    IsWord   \w         Alphanumeric plus _ (Perl)
-   xdigit  IsXDigit [\dA-Fa-f] Hexadecimal digit
+            ASCII-         Full-
+   POSIX    range          range    backslash
+ [[:...:]]  \p{...}        \p{...}   sequence    Description
+
+ -----------------------------------------------------------------------
+ alnum   PosixAlnum       XPosixAlnum            Alpha plus Digit
+ alpha   PosixAlpha       XPosixAlpha            Alphabetic characters
+ ascii   ASCII                                   Any ASCII character
+ blank   PosixBlank       XPosixBlank   \h       Horizontal whitespace;
+                                                   full-range also
+                                                   written as
+                                                   \p{HorizSpace} (GNU
+                                                   extension)
+ cntrl   PosixCntrl       XPosixCntrl            Control characters
+ digit   PosixDigit       XPosixDigit   \d       Decimal digits
+ graph   PosixGraph       XPosixGraph            Alnum plus Punct
+ lower   PosixLower       XPosixLower            Lowercase characters
+ print   PosixPrint       XPosixPrint            Graph plus Print, but
+                                                   not any Cntrls
+ punct   PosixPunct       XPosixPunct            Punctuation and Symbols
+                                                   in ASCII-range; just
+                                                   punct outside it
+ space   PosixSpace       XPosixSpace            [\s\cK]
+         PerlSpace        XPerlSpace    \s       Perl's whitespace def'n
+ upper   PosixUpper       XPosixUpper            Uppercase characters
+ word    PosixWord        XPosixWord    \w       Alnum + Unicode marks +
+                                                   connectors, like '_'
+                                                   (Perl extension)
+ xdigit  ASCII_Hex_Digit  XPosixDigit            Hexadecimal digit,
+                                                    ASCII-range is
+                                                    [0-9A-Fa-f]
+
+Also, various synonyms like C<\p{Alpha}> for C<\p{XPosixAlpha}>; all listed
+in L<perluniprops/Properties accessible through \p{} and \P{}>

 
 Within a character class:
 
 
 Within a character class:
 

-    POSIX       traditional   Unicode
-    [:digit:]       \d        \p{IsDigit}
-    [:^digit:]      \D        \P{IsDigit}
+    POSIX      traditional   Unicode
+  [:digit:]       \d        \p{Digit}
+  [:^digit:]      \D        \P{Digit}

 
 =head2 ANCHORS
 
 
 =head2 ANCHORS
 


@@ -155,49 +204,83 @@ All are zero-width assertions.
    \Z Match string end (before optional newline)
    \z Match absolute string end
    \G Match where previous m//g left off
    \Z Match string end (before optional newline)
    \z Match absolute string end
    \G Match where previous m//g left off

+   \K Keep the stuff left of the \K, don't include it in $&

 
 =head2 QUANTIFIERS
 
 
 =head2 QUANTIFIERS
 

-Quantifiers are greedy by default -- match the B<longest> leftmost.
+Quantifiers are greedy by default and match the B<longest> leftmost.
+
+   Maximal Minimal Possessive Allowed range
+   ------- ------- ---------- -------------
+   {n,m}   {n,m}?  {n,m}+     Must occur at least n times
+                              but no more than m times
+   {n,}    {n,}?   {n,}+      Must occur at least n times
+   {n}     {n}?    {n}+       Must occur exactly n times
+   *       *?      *+         0 or more times (same as {0,})
+   +       +?      ++         1 or more times (same as {1,})
+   ?       ??      ?+         0 or 1 time (same as {0,1})

 
 

-   Maximal Minimal Allowed range
-   ------- ------- -------------
-   {n,m}   {n,m}?  Must occur at least n times but no more than m times
-   {n,}    {n,}?   Must occur at least n times
-   {n}     {n}?    Must occur exactly n times
-   *       *?      0 or more times (same as {0,})
-   +       +?      1 or more times (same as {1,})
-   ?       ??      0 or 1 time (same as {0,1})
+The possessive forms (new in Perl 5.10) prevent backtracking: what gets
+matched by a pattern with a possessive quantifier will not be backtracked
+into, even if that causes the whole match to fail.

 
 

-There is no quantifier {,n} -- that gets understood as a literal string.
+There is no quantifier C<{,n}>. That's interpreted as a literal string.

 
 =head2 EXTENDED CONSTRUCTS
 
 
 =head2 EXTENDED CONSTRUCTS
 

-   (?#text)         A comment
-   (?imxs-imsx:...) Enable/disable option (as per m// modifiers)
-   (?=...)          Zero-width positive lookahead assertion
-   (?!...)          Zero-width negative lookahead assertion
-   (?<=...)         Zero-width positive lookbehind assertion
-   (?<!...)         Zero-width negative lookbehind assertion
-   (?>...)          Grab what we can, prohibit backtracking
-   (?{ code })      Embedded code, return value becomes $^R
-   (??{ code })     Dynamic regex, return value used as regex
-   (?(cond)yes|no)  cond being integer corresponding to capturing parens
-   (?(cond)yes)        or a lookaround/eval zero-width assertion
+   (?#text)          A comment
+   (?:...)           Groups subexpressions without capturing (cluster)
+   (?pimsx-imsx:...) Enable/disable option (as per m// modifiers)
+   (?=...)           Zero-width positive lookahead assertion
+   (?!...)           Zero-width negative lookahead assertion
+   (?<=...)          Zero-width positive lookbehind assertion
+   (?<!...)          Zero-width negative lookbehind assertion
+   (?>...)           Grab what we can, prohibit backtracking
+   (?|...)           Branch reset
+   (?<name>...)      Named capture
+   (?'name'...)      Named capture
+   (?P<name>...)     Named capture (python syntax)
+   (?{ code })       Embedded code, return value becomes $^R
+   (??{ code })      Dynamic regex, return value used as regex
+   (?N)              Recurse into subpattern number N
+   (?-N), (?+N)      Recurse into Nth previous/next subpattern
+   (?R), (?0)        Recurse at the beginning of the whole pattern
+   (?&name)          Recurse into a named subpattern
+   (?P>name)         Recurse into a named subpattern (python syntax)
+   (?(cond)yes|no)
+   (?(cond)yes)      Conditional expression, where "cond" can be:
+                     (?=pat)   look-ahead
+                     (?!pat)   negative look-ahead
+                     (?<=pat)  look-behind
+                     (?<!pat)  negative look-behind
+                     (N)       subpattern N has matched something
+                     (<name>)  named subpattern has matched something
+                     ('name')  named subpattern has matched something
+                     (?{code}) code condition
+                     (R)       true if recursing
+                     (RN)      true if recursing into Nth subpattern
+                     (R&name)  true if recursing into named subpattern
+                     (DEFINE)  always false, no no-pattern allowed

 
 =head2 VARIABLES
 
    $_    Default variable for operators to use
 
 =head2 VARIABLES
 
    $_    Default variable for operators to use

-   $*    Enable multiline matching (deprecated; not in 5.9.0 or later)

 
 

-   $&    Entire matched string

    $`    Everything prior to matched string
    $`    Everything prior to matched string

+   $&    Entire matched string

    $'    Everything after to matched string
 
    $'    Everything after to matched string
 

-The use of those last three will slow down B<all> regex use
-within your program. Consult L<perlvar> for C<@LAST_MATCH_START>
+   ${^PREMATCH}   Everything prior to matched string
+   ${^MATCH}      Entire matched string
+   ${^POSTMATCH}  Everything after to matched string
+
+The use of C<$`>, C<$&> or C<$'> will slow down B<all> regex use
+within your program. Consult L<perlvar> for C<@->

 to see equivalent expressions that won't cause slow down.
 to see equivalent expressions that won't cause slow down.

-See also L<Devel::SawAmpersand>.
+See also L<Devel::SawAmpersand>. Starting with Perl 5.10, you
+can also use the equivalent variables C<${^PREMATCH}>, C<${^MATCH}>
+and C<${^POSTMATCH}>, but for them to be defined, you have to
+specify the C</p> (preserve) modifier on your regular expression.

 
    $1, $2 ...  hold the Xth captured expr
    $+    Last parenthesized pattern match
 
    $1, $2 ...  hold the Xth captured expr
    $+    Last parenthesized pattern match


@@ -205,6 +288,8 @@ See also L<Devel::SawAmpersand>.
    $^R   Holds the result of the last (?{...}) expr
    @-    Offsets of starts of groups. $-[0] holds start of whole match
    @+    Offsets of ends of groups. $+[0] holds end of whole match
    $^R   Holds the result of the last (?{...}) expr
    @-    Offsets of starts of groups. $-[0] holds start of whole match
    @+    Offsets of ends of groups. $+[0] holds end of whole match

+   %+    Named capture groups
+   %-    Named capture groups, as array refs

 
 Captured groups are numbered according to their I<opening> paren.
 
 
 Captured groups are numbered according to their I<opening> paren.
 


@@ -220,25 +305,25 @@ Captured groups are numbered according to their I<opening> paren.
    reset       Reset ?pattern? status
    study       Analyze string for optimizing matching
 
    reset       Reset ?pattern? status
    study       Analyze string for optimizing matching
 

-   split       Use regex to split a string into parts
+   split       Use a regex to split a string into parts

 
 The first four of these are like the escape sequences C<\L>, C<\l>,
 C<\U>, and C<\u>.  For Titlecase, see L</Titlecase>.
 
 
 The first four of these are like the escape sequences C<\L>, C<\l>,
 C<\U>, and C<\u>.  For Titlecase, see L</Titlecase>.
 

-=head2 Terminology
+=head2 TERMINOLOGY

 
 =head3 Titlecase
 
 Unicode concept which most often is equal to uppercase, but for
 certain characters like the German "sharp s" there is a difference.
 
 
 =head3 Titlecase
 
 Unicode concept which most often is equal to uppercase, but for
 certain characters like the German "sharp s" there is a difference.
 

-=head2 AUTHOR
+=head1 AUTHOR

 
 

-Iain Truskett.
+Iain Truskett. Updated by the Perl 5 Porters.

 
 This document may be distributed under the same terms as Perl itself.
 
 
 This document may be distributed under the same terms as Perl itself.
 

-=head2 SEE ALSO
+=head1 SEE ALSO

 
 =over 4
 
 
 =over 4
 


@@ -272,27 +357,35 @@ L<perlfaq6> for FAQs on regular expressions.
 
 =item *
 
 
 =item *
 

+L<perlrebackslash> for a reference on backslash sequences.
+
+=item *
+
+L<perlrecharclass> for a reference on character classes.
+
+=item *
+

 The L<re> module to alter behaviour and aid
 debugging.
 
 =item *
 
 The L<re> module to alter behaviour and aid
 debugging.
 
 =item *
 

-L<perldebug/"Debugging regular expressions">
+L<perldebug/"Debugging Regular Expressions">

 
 =item *
 
 
 =item *
 

-L<perluniintro>, L<perlunicode>, L<charnames> and L<locale>
+L<perluniintro>, L<perlunicode>, L<charnames> and L<perllocale>

 for details on regexes and internationalisation.
 
 =item *
 
 I<Mastering Regular Expressions> by Jeffrey Friedl
 for details on regexes and internationalisation.
 
 =item *
 
 I<Mastering Regular Expressions> by Jeffrey Friedl

-(F<http://regex.info/>) for a thorough grounding and
+(F<http://oreilly.com/catalog/9780596528126/>) for a thorough grounding and

 reference on the topic.
 
 =back
 
 reference on the topic.
 
 =back
 

-=head2 THANKS
+=head1 THANKS

 
 David P.C. Wollmann,
 Richard Soderberg,
 
 David P.C. Wollmann,
 Richard Soderberg,