=head1 DESCRIPTION
-=head2 Important Caveat
+=head2 Important Caveats
-WARNING: The implementation of Unicode support in Perl is incomplete.
+WARNING: While the implementation of Unicode support in Perl is now
+fairly complete it is still evolving to some extent.
-The following areas need further work.
+In particular the way Unicode is handled on EBCDIC platforms is still
+rather experimental. On such a platform references to UTF-8 encoding
+in this document and elsewhere should be read as meaning UTF-EBCDIC as
+specified in Unicode Technical Report 16 unless ASCII vs EBCDIC issues
+are specifically discussed. There is no C<utfebcdic> pragma or
+":utfebcdic" layer, rather "utf8" and ":utf8" are re-used to mean
+platform's "natural" 8-bit encoding of Unicode. See L<perlebcdic> for
+more discussion of the issues.
+
+The following areas are still under development.
=over 4
=item Input and Output Disciplines
-There is currently no easy way to mark data read from a file or other
-external source as being utf8. This will be one of the major areas of
-focus in the near future.
+A filehandle can be marked as containing perl's internal Unicode
+encoding (UTF-8 or UTF-EBCDIC) by opening it with the ":utf8" layer.
+Other encodings can be converted to perl's encoding on input, or from
+perl's encoding on output by use of the ":encoding()" layer. There is
+not yet a clean way to mark the Perl source itself as being in an
+particular encoding.
=item Regular Expressions
-The existing regular expression compiler does not produce polymorphic
-opcodes. This means that the determination on whether to match Unicode
-characters is made when the pattern is compiled, based on whether the
-pattern contains Unicode characters, and not when the matching happens
-at run time. This needs to be changed to adaptively match Unicode if
-the string to be matched is Unicode.
+The regular expression compiler does now attempt to produce
+polymorphic opcodes. That is the pattern should now adapt to the data
+and automatically switch to the Unicode character scheme when
+presented with Unicode data, or a traditional byte scheme when
+presented with byte data. The implementation is still new and
+(particularly on EBCDIC platforms) may need further work.
-=item C<use utf8> still needed to enable a few features
+=item C<use utf8> still needed to enable UTF-8/UTF-EBCDIC in scripts
-The C<utf8> pragma implements the tables used for Unicode support. These
-tables are automatically loaded on demand, so the C<utf8> pragma need not
-normally be used.
+The C<utf8> pragma implements the tables used for Unicode support.
+These tables are automatically loaded on demand, so the C<utf8> pragma
+need not normally be used.
-However, as a compatibility measure, this pragma must be explicitly used
-to enable recognition of UTF-8 encoded literals and identifiers in the
-source text.
+However, as a compatibility measure, this pragma must be explicitly
+used to enable recognition of UTF-8 in the Perl scripts themselves on
+ASCII based machines or recognize UTF-EBCDIC on EBCDIC based machines.
+B<NOTE: this should be the only place where an explicit C<use utf8> is
+needed>.
=back
Beginning with version 5.6, Perl uses logically wide characters to
represent strings internally. This internal representation of strings
-uses the UTF-8 encoding.
+uses either the UTF-8 or the UTF-EBCDIC encoding.
-In future, Perl-level operations can be expected to work with characters
-rather than bytes, in general.
+In future, Perl-level operations can be expected to work with
+characters rather than bytes, in general.
-However, as strictly an interim compatibility measure, Perl v5.6 aims to
-provide a safe migration path from byte semantics to character semantics
-for programs. For operations where Perl can unambiguously decide that the
-input data is characters, Perl now switches to character semantics.
-For operations where this determination cannot be made without additional
-information from the user, Perl decides in favor of compatibility, and
-chooses to use byte semantics.
+However, as strictly an interim compatibility measure, Perl aims to
+provide a safe migration path from byte semantics to character
+semantics for programs. For operations where Perl can unambiguously
+decide that the input data is characters, Perl now switches to
+character semantics. For operations where this determination cannot
+be made without additional information from the user, Perl decides in
+favor of compatibility, and chooses to use byte semantics.
This behavior preserves compatibility with earlier versions of Perl,
which allowed byte semantics in Perl operations, but only as long as
external programs, from information provided by the system (such as %ENV),
or from literals and constants in the source text.
-If the C<-C> command line switch is used, (or the ${^WIDE_SYSTEM_CALLS}
-global flag is set to C<1>), all system calls will use the
-corresponding wide character APIs. This is currently only implemented
-on Windows.
+If the C<-C> command line switch is used, (or the
+${^WIDE_SYSTEM_CALLS} global flag is set to C<1>), all system calls
+will use the corresponding wide character APIs. Note that this is
+currently only implemented on Windows since other platforms API
+standard on this area.
-Regardless of the above, the C<bytes> pragma can always be used to force
-byte semantics in a particular lexical scope. See L<bytes>.
+Regardless of the above, the C<bytes> pragma can always be used to
+force byte semantics in a particular lexical scope. See L<bytes>.
The C<utf8> pragma is primarily a compatibility device that enables
-recognition of UTF-8 in literals encountered by the parser. It may also
-be used for enabling some of the more experimental Unicode support features.
+recognition of UTF-(8|EBCDIC) in literals encountered by the parser.
Note that this pragma is only required until a future version of Perl
in which character semantics will become the default. This pragma may
then become a no-op. See L<utf8>.
apply; otherwise, byte semantics are in effect. To force byte semantics
on Unicode data, the C<bytes> pragma should be used.
+Notice that if you have a string with byte semantics and you then
+add character data into it, the bytes will be upgraded I<as if they
+were ISO 8859-1 (Latin-1)> (or if in EBCDIC, after a translation
+to ISO 8859-1).
+
Under character semantics, many operations that formerly operated on
-bytes change to operating on characters. For ASCII data this makes
-no difference, because UTF-8 stores ASCII in single bytes, but for
-any character greater than C<chr(127)>, the character may be stored in
+bytes change to operating on characters. For ASCII data this makes no
+difference, because UTF-8 stores ASCII in single bytes, but for any
+character greater than C<chr(127)>, the character B<may> be stored in
a sequence of two or more bytes, all of which have the high bit set.
-But by and large, the user need not worry about this, because Perl
-hides it from the user. A character in Perl is logically just a number
-ranging from 0 to 2**32 or so. Larger characters encode to longer
-sequences of bytes internally, but again, this is just an internal
-detail which is hidden at the Perl level.
+
+For C1 controls or Latin 1 characters on an EBCDIC platform the
+character may be stored in a UTF-EBCDIC multi byte sequence. But by
+and large, the user need not worry about this, because Perl hides it
+from the user. A character in Perl is logically just a number ranging
+from 0 to 2**32 or so. Larger characters encode to longer sequences
+of bytes internally, but again, this is just an internal detail which
+is hidden at the Perl level.
=head2 Effects of character semantics
Strings and patterns may contain characters that have an ordinal value
larger than 255.
-Presuming you use a Unicode editor to edit your program, such characters
-will typically occur directly within the literal strings as UTF-8
-characters, but you can also specify a particular character with an
-extension of the C<\x> notation. UTF-8 characters are specified by
-putting the hexadecimal code within curlies after the C<\x>. For instance,
-a Unicode smiley face is C<\x{263A}>.
+Presuming you use a Unicode editor to edit your program, such
+characters will typically occur directly within the literal strings as
+UTF-8 (or UTF-EBCDIC on EBCDIC platforms) characters, but you can also
+specify a particular character with an extension of the C<\x>
+notation. UTF-X characters are specified by putting the hexadecimal
+code within curlies after the C<\x>. For instance, a Unicode smiley
+face is C<\x{263A}>.
=item *
Identifiers within the Perl script may contain Unicode alphanumeric
characters, including ideographs. (You are currently on your own when
-it comes to using the canonical forms of characters--Perl doesn't (yet)
-attempt to canonicalize variable names for you.)
+it comes to using the canonical forms of characters--Perl doesn't
+(yet) attempt to canonicalize variable names for you.)
=item *
Regular expressions match characters instead of bytes. For instance,
"." matches a character instead of a byte. (However, the C<\C> pattern
-is provided to force a match a single byte ("C<char>" in C, hence
-C<\C>).)
+is provided to force a match a single byte ("C<char>" in C, hence C<\C>).)
=item *
Character classes in regular expressions match characters instead of
bytes, and match against the character properties specified in the
-Unicode properties database. So C<\w> can be used to match an ideograph,
-for instance.
+Unicode properties database. So C<\w> can be used to match an
+ideograph, for instance.
=item *
classes via the new C<\p{}> (matches property) and C<\P{}> (doesn't
match property) constructs. For instance, C<\p{Lu}> matches any
character with the Unicode uppercase property, while C<\p{M}> matches
-any mark character. Single letter properties may omit the brackets, so
-that can be written C<\pM> also. Many predefined character classes are
-available, such as C<\p{IsMirrored}> and C<\p{InTibetan}>.
+any mark character. Single letter properties may omit the brackets,
+so that can be written C<\pM> also. Many predefined character classes
+are available, such as C<\p{IsMirrored}> and C<\p{InTibetan}>.
+
+The C<\p{Is...}> test for "general properties" such as "letter",
+"digit", while the C<\p{In...}> test for Unicode scripts and blocks.
+
+The official Unicode script and block names have spaces and
+dashes and separators, but for convenience you can have
+dashes, spaces, and underbars at every word division, and
+you need not care about correct casing. It is recommended,
+however, that for consistency you use the following naming:
+the official Unicode script or block name (see below for
+the additional rules that apply to block names), with the whitespace
+and dashes removed, and the words "uppercase-first-lowercase-otherwise".
+That is, "Latin-1 Supplement" becomes "Latin1Supplement".
+
+You can also negate both C<\p{}> and C<\P{}> by introducing a caret
+(^) between the first curly and the property name: C<\p{^InTamil}> is
+equal to C<\P{InTamil}>.
+
+The C<In> and C<Is> can be left out: C<\p{Greek}> is equal to
+C<\p{InGreek}>, C<\P{Pd}> is equal to C<\P{Pd}>.
+
+ Short Long
+
+ L Letter
+ Lu Uppercase Letter
+ Ll Lowercase Letter
+ Lt Titlecase Letter
+ Lm Modifier Letter
+ Lo Other Letter
+
+ M Mark
+ Mn Non-Spacing Mark
+ Mc Spacing Combining Mark
+ Me Enclosing Mark
+
+ N Number
+ Nd Decimal Digit Number
+ Nl Letter Number
+ No Other Number
+
+ P Punctuation
+ Pc Connector Punctuation
+ Pd Dash Punctuation
+ Ps Open Punctuation
+ Pe Close Punctuation
+ Pi Initial Punctuation
+ (may behave like Ps or Pe depending on usage)
+ Pf Final Punctuation
+ (may behave like Ps or Pe depending on usage)
+ Po Other Punctuation
+
+ S Symbol
+ Sm Math Symbol
+ Sc Currency Symbol
+ Sk Modifier Symbol
+ So Other Symbol
+
+ Z Separator
+ Zs Space Separator
+ Zl Line Separator
+ Zp Paragraph Separator
+
+ C Other
+ Cc (Other) Control
+ Cf (Other) Format
+ Cs (Other) Surrogate
+ Co (Other) Private Use
+ Cn (Other) Not Assigned
+
+There's also C<L&> which is an alias for C<Ll>, C<Lu>, and C<Lt>.
+
+The following reserved ranges have C<In> tests:
+
+ CJK Ideograph Extension A
+ CJK Ideograph
+ Hangul Syllable
+ Non Private Use High Surrogate
+ Private Use High Surrogate
+ Low Surrogate
+ Private Surrogate
+ CJK Ideograph Extension B
+ Plane 15 Private Use
+ Plane 16 Private Use
+
+For example C<"\x{AC00}" =~ \p{HangulSyllable}> will test true.
+(Handling of surrogates is not implemented yet, because Perl
+uses UTF-8 and not UTF-16 internally to represent Unicode.)
+
+Additionally, because scripts differ in their directionality
+(for example Hebrew is written right to left), all characters
+have their directionality defined:
+
+ BidiL Left-to-Right
+ BidiLRE Left-to-Right Embedding
+ BidiLRO Left-to-Right Override
+ BidiR Right-to-Left
+ BidiAL Right-to-Left Arabic
+ BidiRLE Right-to-Left Embedding
+ BidiRLO Right-to-Left Override
+ BidiPDF Pop Directional Format
+ BidiEN European Number
+ BidiES European Number Separator
+ BidiET European Number Terminator
+ BidiAN Arabic Number
+ BidiCS Common Number Separator
+ BidiNSM Non-Spacing Mark
+ BidiBN Boundary Neutral
+ BidiB Paragraph Separator
+ BidiS Segment Separator
+ BidiWS Whitespace
+ BidiON Other Neutrals
+
+=head2 Scripts
+
+The scripts available for C<\p{In...}> and C<\P{In...}>, for example
+\p{InCyrillic>, are as follows, for example C<\p{InLatin}> or C<\P{InHan}>:
+
+ Arabic
+ Armenian
+ Bengali
+ Bopomofo
+ Canadian-Aboriginal
+ Cherokee
+ Cyrillic
+ Deseret
+ Devanagari
+ Ethiopic
+ Georgian
+ Gothic
+ Greek
+ Gujarati
+ Gurmukhi
+ Han
+ Hangul
+ Hebrew
+ Hiragana
+ Inherited
+ Kannada
+ Katakana
+ Khmer
+ Lao
+ Latin
+ Malayalam
+ Mongolian
+ Myanmar
+ Ogham
+ Old-Italic
+ Oriya
+ Runic
+ Sinhala
+ Syriac
+ Tamil
+ Telugu
+ Thaana
+ Thai
+ Tibetan
+ Yi
+
+There are also extended property classes that supplement the basic
+properties, defined by the F<PropList> Unicode database:
+
+ ASCII_Hex_Digit
+ Bidi_Control
+ Dash
+ Diacritic
+ Extender
+ Hex_Digit
+ Hyphen
+ Ideographic
+ Join_Control
+ Noncharacter_Code_Point
+ Other_Alphabetic
+ Other_Lowercase
+ Other_Math
+ Other_Uppercase
+ Quotation_Mark
+ White_space
+
+and further derived properties:
+
+ Alphabetic Lu + Ll + Lt + Lm + Lo + Other_Alphabetic
+ Lowercase Ll + Other_Lowercase
+ Uppercase Lu + Other_Uppercase
+ Math Sm + Other_Math
+
+ ID_Start Lu + Ll + Lt + Lm + Lo + Nl
+ ID_Continue ID_Start + Mn + Mc + Nd + Pc
+
+ Any Any character
+ Assigned Any non-Cn character
+ Common Any character (or unassigned code point)
+ not explicitly assigned to a script.
+
+=head2 Blocks
+
+In addition to B<scripts>, Unicode also defines B<blocks> of
+characters. The difference between scripts and blocks is that the
+scripts concept is closer to natural languages, while the blocks
+concept is more an artificial grouping based on groups of 256 Unicode
+characters. For example, the C<Latin> script contains letters from
+many blocks. On the other hand, the C<Latin> script does not contain
+all the characters from those blocks, it does not for example contain
+digits because digits are shared across many scripts. Digits and
+other similar groups, like punctuation, are in a category called
+C<Common>.
+
+For more about scripts see the UTR #24:
+http://www.unicode.org/unicode/reports/tr24/
+For more about blocks see
+http://www.unicode.org/Public/UNIDATA/Blocks.txt
+
+Because there are overlaps in naming (there are, for example, both
+a script called C<Katakana> and a block called C<Katakana>, the block
+version has C<Block> appended to its name, C<\p{InKatakanaBlock}>.
+
+Notice that this definition was introduced in Perl 5.8.0: in Perl
+5.6.0 only the blocks were used; in Perl 5.8.0 scripts became the
+preferential Unicode character class definition; this meant that
+the definitions of some character classes changed (the ones in the
+below list that have the C<Block> appended).
+
+ Alphabetic Presentation Forms
+ Arabic Block
+ Arabic Presentation Forms-A
+ Arabic Presentation Forms-B
+ Armenian Block
+ Arrows
+ Basic Latin
+ Bengali Block
+ Block Elements
+ Bopomofo Block
+ Bopomofo Extended
+ Box Drawing
+ Braille Patterns
+ Byzantine Musical Symbols
+ CJK Compatibility
+ CJK Compatibility Forms
+ CJK Compatibility Ideographs
+ CJK Compatibility Ideographs Supplement
+ CJK Radicals Supplement
+ CJK Symbols and Punctuation
+ CJK Unified Ideographs
+ CJK Unified Ideographs Extension A
+ CJK Unified Ideographs Extension B
+ Cherokee Block
+ Combining Diacritical Marks
+ Combining Half Marks
+ Combining Marks for Symbols
+ Control Pictures
+ Currency Symbols
+ Cyrillic Block
+ Deseret Block
+ Devanagari Block
+ Dingbats
+ Enclosed Alphanumerics
+ Enclosed CJK Letters and Months
+ Ethiopic Block
+ General Punctuation
+ Geometric Shapes
+ Georgian Block
+ Gothic Block
+ Greek Block
+ Greek Extended
+ Gujarati Block
+ Gurmukhi Block
+ Halfwidth and Fullwidth Forms
+ Hangul Compatibility Jamo
+ Hangul Jamo
+ Hangul Syllables
+ Hebrew Block
+ High Private Use Surrogates
+ High Surrogates
+ Hiragana Block
+ IPA Extensions
+ Ideographic Description Characters
+ Kanbun
+ Kangxi Radicals
+ Kannada Block
+ Katakana Block
+ Khmer Block
+ Lao Block
+ Latin 1 Supplement
+ Latin Extended Additional
+ Latin Extended-A
+ Latin Extended-B
+ Letterlike Symbols
+ Low Surrogates
+ Malayalam Block
+ Mathematical Alphanumeric Symbols
+ Mathematical Operators
+ Miscellaneous Symbols
+ Miscellaneous Technical
+ Mongolian Block
+ Musical Symbols
+ Myanmar Block
+ Number Forms
+ Ogham Block
+ Old Italic Block
+ Optical Character Recognition
+ Oriya Block
+ Private Use
+ Runic Block
+ Sinhala Block
+ Small Form Variants
+ Spacing Modifier Letters
+ Specials
+ Superscripts and Subscripts
+ Syriac Block
+ Tags
+ Tamil Block
+ Telugu Block
+ Thaana Block
+ Thai Block
+ Tibetan Block
+ Unified Canadian Aboriginal Syllabics
+ Yi Radicals
+ Yi Syllables
=item *
=item *
Case translation operators use the Unicode case translation tables
-when provided character input. Note that C<uc()> translates to
-uppercase, while C<ucfirst> translates to titlecase (for languages
-that make the distinction). Naturally the corresponding backslash
-sequences have the same semantics.
+when provided character input. Note that C<uc()> (also known as C<\U>
+in doublequoted strings) translates to uppercase, while C<ucfirst>
+(also known as C<\u> in doublequoted strings) translates to titlecase
+(for languages that make the distinction). Naturally the
+corresponding backslash sequences have the same semantics.
=item *
Most operators that deal with positions or lengths in the string will
-automatically switch to using character positions, including C<chop()>,
-C<substr()>, C<pos()>, C<index()>, C<rindex()>, C<sprintf()>,
-C<write()>, and C<length()>. Operators that specifically don't switch
-include C<vec()>, C<pack()>, and C<unpack()>. Operators that really
-don't care include C<chomp()>, as well as any other operator that
-treats a string as a bucket of bits, such as C<sort()>, and the
-operators dealing with filenames.
+automatically switch to using character positions, including
+C<chop()>, C<substr()>, C<pos()>, C<index()>, C<rindex()>,
+C<sprintf()>, C<write()>, and C<length()>. Operators that
+specifically don't switch include C<vec()>, C<pack()>, and
+C<unpack()>. Operators that really don't care include C<chomp()>, as
+well as any other operator that treats a string as a bucket of bits,
+such as C<sort()>, and the operators dealing with filenames.
=item *
The C<chr()> and C<ord()> functions work on characters. This is like
C<pack("U")> and C<unpack("U")>, not like C<pack("C")> and
C<unpack("C")>. In fact, the latter are how you now emulate
-byte-oriented C<chr()> and C<ord()> under utf8.
+byte-oriented C<chr()> and C<ord()> for Unicode strings.
+(Note that this reveals the internal UTF-8 encoding of strings and
+you are not supposed to do that unless you know what you are doing.)
=item *
The bit string operators C<& | ^ ~> can operate on character data.
However, for backward compatibility reasons (bit string operations
-when the characters all are less than 256 in ordinal value) one cannot
-mix C<~> (the bit complement) and characters both less than 256 and
+when the characters all are less than 256 in ordinal value) one should
+not mix C<~> (the bit complement) and characters both less than 256 and
equal or greater than 256. Most importantly, the DeMorgan's laws
(C<~($x|$y) eq ~$x&~$y>, C<~($x&$y) eq ~$x|~$y>) won't hold.
Another way to look at this is that the complement cannot return
-B<both> the 8-bit (byte) wide bit complement, and the full character
+B<both> the 8-bit (byte) wide bit complement B<and> the full character
wide bit complement.
=item *
+lc(), uc(), lcfirst(), and ucfirst() work for the following cases:
+
+=over 8
+
+=item *
+
+the case mapping is from a single Unicode character to another
+single Unicode character
+
+=item *
+
+the case mapping is from a single Unicode character to more
+than one Unicode character
+
+=back
+
+What doesn't yet work are the followng cases:
+
+=over 8
+
+=item *
+
+the "final sigma" (Greek)
+
+=item *
+
+anything to with locales (Lithuanian, Turkish, Azeri)
+
+=back
+
+See the Unicode Technical Report #21, Case Mappings, for more details.
+
+=item *
+
And finally, C<scalar reverse()> reverses by character rather than by byte.
=back
=head2 Character encodings for input and output
-[XXX: This feature is not yet implemented.]
+See L<Encode>.
=head1 CAVEATS
As of yet, there is no method for automatically coercing input and
-output to some encoding other than UTF-8. This is planned in the near
-future, however.
+output to some encoding other than UTF-8 or UTF-EBCDIC. This is planned
+in the near future, however.
Whether an arbitrary piece of data will be treated as "characters" or
"bytes" by internal operations cannot be divined at the current time.
characters above that range (when mapped into Unicode). It will also
tend to run slower. Avoidance of locales is strongly encouraged.
+=head1 UNICODE REGULAR EXPRESSION SUPPORT LEVEL
+
+The following list of Unicode regular expression support describes
+feature by feature the Unicode support implemented in Perl as of Perl
+5.8.0. The "Level N" and the section numbers refer to the Unicode
+Technical Report 18, "Unicode Regular Expression Guidelines".
+
+=over 4
+
+=item *
+
+Level 1 - Basic Unicode Support
+
+ 2.1 Hex Notation - done [1]
+ Named Notation - done [2]
+ 2.2 Categories - done [3][4]
+ 2.3 Subtraction - MISSING [5][6]
+ 2.4 Simple Word Boundaries - done [7]
+ 2.5 Simple Loose Matches - MISSING [8]
+ 2.6 End of Line - MISSING [9][10]
+
+ [ 1] \x{...}
+ [ 2] \N{...}
+ [ 3] . \p{Is...} \P{Is...}
+ [ 4] now scripts (see UTR#24 Script Names) in addition to blocks
+ [ 5] have negation
+ [ 6] can use look-ahead to emulate subtracion
+ [ 7] include Letters in word characters
+ [ 8] see UTR#21 Case Mappings
+ [ 9] see UTR#13 Unicode Newline Guidelines
+ [10] should do ^ and $ also on \x{2028} and \x{2029}
+
+=item *
+
+Level 2 - Extended Unicode Support
+
+ 3.1 Surrogates - MISSING
+ 3.2 Canonical Equivalents - MISSING [11][12]
+ 3.3 Locale-Independent Graphemes - MISSING [13]
+ 3.4 Locale-Independent Words - MISSING [14]
+ 3.5 Locale-Independent Loose Matches - MISSING [15]
+
+ [11] see UTR#15 Unicode Normalization
+ [12] have Unicode::Normalize but not integrated to regexes
+ [13] have \X but at this level . should equal that
+ [14] need three classes, not just \w and \W
+ [15] see UTR#21 Case Mappings
+
+=item *
+
+Level 3 - Locale-Sensitive Support
+
+ 4.1 Locale-Dependent Categories - MISSING
+ 4.2 Locale-Dependent Graphemes - MISSING [16][17]
+ 4.3 Locale-Dependent Words - MISSING
+ 4.4 Locale-Dependent Loose Matches - MISSING
+ 4.5 Locale-Dependent Ranges - MISSING
+
+ [16] see UTR#10 Unicode Collation Algorithms
+ [17] have Unicode::Collate but not integrated to regexes
+
+=back
+
=head1 SEE ALSO
-L<bytes>, L<utf8>, L<perlvar/"${^WIDE_SYSTEM_CALLS}">
+L<bytes>, L<utf8>, L<perlretut>, L<perlvar/"${^WIDE_SYSTEM_CALLS}">
=cut
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