=item *
-Strings and patterns may contain characters that have an ordinal value
-larger than 255.
+Strings (including hash keys) and regular expression patterns may
+contain characters that have an ordinal value larger than 255.
If you use a Unicode editor to edit your program, Unicode characters
may occur directly within the literal strings in one of the various
This works only for characters with a code 0x100 and above.
Additionally, if you
+
use charnames ':full';
+
you can use the C<\N{...}> notation, putting the official Unicode character
name within the curlies. For example, C<\N{WHITE SMILING FACE}>.
This works for all characters that have names.
=item *
-If an appropriate L<encoding> is specified,
-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.)
+If an appropriate L<encoding> is specified, 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.)
=item *
=head2 Scripts
The scripts available via C<\p{...}> and C<\P{...}>, for example
-C<\p{Latin}> or \p{Cyrillic>, are as follows:
+C<\p{Latin}> or C<\p{Cyrillic}>, are as follows:
Arabic
Armenian
Bengali
Bopomofo
+ Buhid
CanadianAboriginal
Cherokee
Cyrillic
Gurmukhi
Han
Hangul
+ Hanunoo
Hebrew
Hiragana
Inherited
Runic
Sinhala
Syriac
+ Tagalog
+ Tagbanwa
Tamil
Telugu
Thaana
There are also extended property classes that supplement the basic
properties, defined by the F<PropList> Unicode database:
- ASCII_Hex_Digit
+ ASCIIHexDigit
BidiControl
Dash
+ Deprecated
Diacritic
Extender
+ GraphemeLink
HexDigit
Hyphen
Ideographic
+ IDSBinaryOperator
+ IDSTrinaryOperator
JoinControl
+ LogicalOrderException
NoncharacterCodePoint
OtherAlphabetic
+ OtherDefaultIgnorableCodePoint
+ OtherGraphemeExtend
OtherLowercase
OtherMath
OtherUppercase
QuotationMark
+ Radical
+ SoftDotted
+ TerminalPunctuation
+ UnifiedIdeograph
WhiteSpace
and further derived properties:
ID_Continue ID_Start + Mn + Mc + Nd + Pc
Any Any character
- Assigned Any non-Cn character (i.e. synonym for C<\P{Cn}>)
- Unassigned Synonym for C<\p{Cn}>
+ Assigned Any non-Cn character (i.e. synonym for \P{Cn})
+ Unassigned Synonym for \p{Cn}
Common Any character (or unassigned code point)
not explicitly assigned to a script
-For backward compatability, all properties mentioned so far may have C<Is>
+For backward compatibility, all properties mentioned so far may have C<Is>
prepended to their name (e.g. C<\P{IsLu}> is equal to C<\P{Lu}>).
=head2 Blocks
Blocks names are given with the C<In> prefix. For example, the
Katakana block is referenced via C<\p{InKatakana}>. The C<In>
-prefix may be omitted if there is no nameing conflict with a script
+prefix may be omitted if there is no naming conflict with a script
or any other property, but it is recommended that C<In> always be used
to avoid confusion.
These block names are supported:
- InAlphabeticPresentationForms
- InArabicBlock
- InArabicPresentationFormsA
- InArabicPresentationFormsB
- InArmenianBlock
- InArrows
- InBasicLatin
- InBengaliBlock
- InBlockElements
- InBopomofoBlock
- InBopomofoExtended
- InBoxDrawing
- InBraillePatterns
- InByzantineMusicalSymbols
- InCJKCompatibility
- InCJKCompatibilityForms
- InCJKCompatibilityIdeographs
- InCJKCompatibilityIdeographsSupplement
- InCJKRadicalsSupplement
- InCJKSymbolsAndPunctuation
- InCJKUnifiedIdeographs
- InCJKUnifiedIdeographsExtensionA
- InCJKUnifiedIdeographsExtensionB
- InCherokeeBlock
- InCombiningDiacriticalMarks
- InCombiningHalfMarks
- InCombiningMarksForSymbols
- InControlPictures
- InCurrencySymbols
- InCyrillicBlock
- InDeseretBlock
- InDevanagariBlock
- InDingbats
- InEnclosedAlphanumerics
- InEnclosedCJKLettersAndMonths
- InEthiopicBlock
- InGeneralPunctuation
- InGeometricShapes
- InGeorgianBlock
- InGothicBlock
- InGreekBlock
- InGreekExtended
- InGujaratiBlock
- InGurmukhiBlock
- InHalfwidthAndFullwidthForms
- InHangulCompatibilityJamo
- InHangulJamo
- InHangulSyllables
- InHebrewBlock
- InHighPrivateUseSurrogates
- InHighSurrogates
- InHiraganaBlock
- InIPAExtensions
- InIdeographicDescriptionCharacters
- InKanbun
- InKangxiRadicals
- InKannadaBlock
- InKatakanaBlock
- InKhmerBlock
- InLaoBlock
- InLatin1Supplement
- InLatinExtendedAdditional
- InLatinExtended-A
- InLatinExtended-B
- InLetterlikeSymbols
- InLowSurrogates
- InMalayalamBlock
- InMathematicalAlphanumericSymbols
- InMathematicalOperators
- InMiscellaneousSymbols
- InMiscellaneousTechnical
- InMongolianBlock
- InMusicalSymbols
- InMyanmarBlock
- InNumberForms
- InOghamBlock
- InOldItalicBlock
- InOpticalCharacterRecognition
- InOriyaBlock
- InPrivateUse
- InRunicBlock
- InSinhalaBlock
- InSmallFormVariants
- InSpacingModifierLetters
- InSpecials
- InSuperscriptsAndSubscripts
- InSyriacBlock
- InTags
- InTamilBlock
- InTeluguBlock
- InThaanaBlock
- InThaiBlock
- InTibetanBlock
- InUnifiedCanadianAboriginalSyllabics
- InYiRadicals
- InYiSyllables
+ InAlphabeticPresentationForms
+ InArabic
+ InArabicPresentationFormsA
+ InArabicPresentationFormsB
+ InArmenian
+ InArrows
+ InBasicLatin
+ InBengali
+ InBlockElements
+ InBopomofo
+ InBopomofoExtended
+ InBoxDrawing
+ InBraillePatterns
+ InBuhid
+ InByzantineMusicalSymbols
+ InCJKCompatibility
+ InCJKCompatibilityForms
+ InCJKCompatibilityIdeographs
+ InCJKCompatibilityIdeographsSupplement
+ InCJKRadicalsSupplement
+ InCJKSymbolsAndPunctuation
+ InCJKUnifiedIdeographs
+ InCJKUnifiedIdeographsExtensionA
+ InCJKUnifiedIdeographsExtensionB
+ InCherokee
+ InCombiningDiacriticalMarks
+ InCombiningDiacriticalMarksforSymbols
+ InCombiningHalfMarks
+ InControlPictures
+ InCurrencySymbols
+ InCyrillic
+ InCyrillicSupplementary
+ InDeseret
+ InDevanagari
+ InDingbats
+ InEnclosedAlphanumerics
+ InEnclosedCJKLettersAndMonths
+ InEthiopic
+ InGeneralPunctuation
+ InGeometricShapes
+ InGeorgian
+ InGothic
+ InGreekExtended
+ InGreekAndCoptic
+ InGujarati
+ InGurmukhi
+ InHalfwidthAndFullwidthForms
+ InHangulCompatibilityJamo
+ InHangulJamo
+ InHangulSyllables
+ InHanunoo
+ InHebrew
+ InHighPrivateUseSurrogates
+ InHighSurrogates
+ InHiragana
+ InIPAExtensions
+ InIdeographicDescriptionCharacters
+ InKanbun
+ InKangxiRadicals
+ InKannada
+ InKatakana
+ InKatakanaPhoneticExtensions
+ InKhmer
+ InLao
+ InLatin1Supplement
+ InLatinExtendedA
+ InLatinExtendedAdditional
+ InLatinExtendedB
+ InLetterlikeSymbols
+ InLowSurrogates
+ InMalayalam
+ InMathematicalAlphanumericSymbols
+ InMathematicalOperators
+ InMiscellaneousMathematicalSymbolsA
+ InMiscellaneousMathematicalSymbolsB
+ InMiscellaneousSymbols
+ InMiscellaneousTechnical
+ InMongolian
+ InMusicalSymbols
+ InMyanmar
+ InNumberForms
+ InOgham
+ InOldItalic
+ InOpticalCharacterRecognition
+ InOriya
+ InPrivateUseArea
+ InRunic
+ InSinhala
+ InSmallFormVariants
+ InSpacingModifierLetters
+ InSpecials
+ InSuperscriptsAndSubscripts
+ InSupplementalArrowsA
+ InSupplementalArrowsB
+ InSupplementalMathematicalOperators
+ InSupplementaryPrivateUseAreaA
+ InSupplementaryPrivateUseAreaB
+ InSyriac
+ InTagalog
+ InTagbanwa
+ InTags
+ InTamil
+ InTelugu
+ InThaana
+ InThai
+ InTibetan
+ InUnifiedCanadianAboriginalSyllabics
+ InVariationSelectors
+ InYiRadicals
+ InYiSyllables
=over 4
=item *
-The special pattern C<\X> match matches any extended Unicode sequence
+The special pattern C<\X> matches any extended Unicode sequence
(a "combining character sequence" in Standardese), where the first
character is a base character and subsequent characters are mark
characters that apply to the base character. It is equivalent to
See L<Encode>.
-=head1 CAVEATS
-
-Whether an arbitrary piece of data will be treated as "characters" or
-"bytes" by internal operations cannot be divined at the current time.
-
-Use of locales with Unicode data may lead to odd results. Currently
-there is some attempt to apply 8-bit locale info to characters in the
-range 0..255, but this is demonstrably incorrect for locales that use
-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
+=head2 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
in Perl can be written as:
- (?!\p{Unassigned})\p{InGreek}
- (?=\p{Assigned})\p{InGreek}
+ (?!\p{Unassigned})\p{InGreekAndCoptic}
+ (?=\p{Assigned})\p{InGreekAndCoptic}
But in this particular example, you probably really want
=over 4
-=item
+=item *
UTF-8
require 4 bytes), byteorder independent encoding. For ASCII, UTF-8 is
transparent (and we really do mean 7-bit ASCII, not another 8-bit encoding).
-The following table is from Unicode 3.1.
+The following table is from Unicode 3.2.
Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte
- U+0000..U+007F 00..7F
- U+0080..U+07FF C2..DF 80..BF
+ U+0000..U+007F 00..7F
+ U+0080..U+07FF C2..DF 80..BF
U+0800..U+0FFF E0 A0..BF 80..BF
- U+1000..U+FFFF E1..EF 80..BF 80..BF
+ U+1000..U+CFFF E1..EC 80..BF 80..BF
+ U+D000..U+D7FF ED 80..9F 80..BF
+ U+D800..U+DFFF ******* ill-formed *******
+ U+E000..U+FFFF EE..EF 80..BF 80..BF
U+10000..U+3FFFF F0 90..BF 80..BF 80..BF
U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF
U+100000..U+10FFFF F4 80..8F 80..BF 80..BF
+Note the A0..BF in U+0800..U+0FFF, the 80..9F in U+D000...U+D7FF,
+the 90..BF in U+10000..U+3FFFF, and the 80...8F in U+100000..U+10FFFF.
+The "gaps" are caused by legal UTF-8 avoiding non-shortest encodings:
+it is technically possible to UTF-8-encode a single code point in different
+ways, but that is explicitly forbidden, and the shortest possible encoding
+should always be used (and that is what Perl does).
+
Or, another way to look at it, as bits:
Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte
00000dddccccccbbbbbbaaaaaa 11110ddd 10cccccc 10bbbbbb 10aaaaaa
As you can see, the continuation bytes all begin with C<10>, and the
-leading bits of the start byte tells how many bytes the are in the
+leading bits of the start byte tell how many bytes the are in the
encoded character.
-=item
+=item *
UTF-EBCDIC
Like UTF-8, but EBCDIC-safe, as UTF-8 is ASCII-safe.
-=item
+=item *
UTF-16, UTF-16BE, UTF16-LE, Surrogates, and BOMs (Byte Order Marks)
and the decoding is
- $uni = 0x10000 + ($hi - 0xD8000) * 0x400 + ($lo - 0xDC00);
+ $uni = 0x10000 + ($hi - 0xD800) * 0x400 + ($lo - 0xDC00);
If you try to generate surrogates (for example by using chr()), you
will get a warning if warnings are turned on (C<-w> or C<use
little-endian format" and cannot be "0xFFFE, represented in big-endian
format".
-=item
+=item *
UTF-32, UTF-32BE, UTF32-LE
needed. The BOM signatures will be 0x00 0x00 0xFE 0xFF for BE and
0xFF 0xFE 0x00 0x00 for LE.
-=item
+=item *
UCS-2, UCS-4
encoding, UCS-4 is a 32-bit encoding. Unlike UTF-16, UCS-2
is not extensible beyond 0xFFFF, because it does not use surrogates.
-=item
+=item *
UTF-7
=back
-=head2 Security Implications of Malformed UTF-8
+=head2 Security Implications of Unicode
+
+=over 4
+
+=item *
+
+Malformed UTF-8
Unfortunately, the specification of UTF-8 leaves some room for
interpretation of how many bytes of encoded output one should generate
malformations, too, such as the surrogates, which are not real
Unicode code points.)
+=item *
+
+Regular expressions behave slightly differently between byte data and
+character (Unicode data). For example, the "word character" character
+class C<\w> will work differently when the data is all eight-bit bytes
+or when the data is Unicode.
+
+In the first case, the set of C<\w> characters is either small (the
+default set of alphabetic characters, digits, and the "_"), or, if you
+are using a locale (see L<perllocale>), the C<\w> might contain a few
+more letters according to your language and country.
+
+In the second case, the C<\w> set of characters is much, much larger,
+and most importantly, even in the set of the first 256 characters, it
+will most probably be different: as opposed to most locales (which are
+specific to a language and country pair) Unicode classifies all the
+characters that are letters as C<\w>. For example: your locale might
+not think that LATIN SMALL LETTER ETH is a letter (unless you happen
+to speak Icelandic), but Unicode does.
+
+As discussed elsewhere, Perl tries to stand one leg (two legs, as
+camels are quadrupeds?) in two worlds: the old world of bytes and the new
+world of characters, upgrading from bytes to characters when necessary.
+If your legacy code is not explicitly using Unicode, no automatic
+switchover to characters should happen, and characters shouldn't get
+downgraded back to bytes, either. It is possible to accidentally mix
+bytes and characters, however (see L<perluniintro>), in which case the
+C<\w> might start behaving differently. Review your code.
+
+=back
+
=head2 Unicode in Perl on EBCDIC
The way Unicode is handled on EBCDIC platforms is still rather
the platform's "natural" 8-bit encoding of Unicode. See L<perlebcdic>
for more discussion of the issues.
+=head2 Locales
+
+Usually locale settings and Unicode do not affect each other, but
+there are a couple of exceptions:
+
+=over 4
+
+=item *
+
+If your locale environment variables (LANGUAGE, LC_ALL, LC_CTYPE, LANG)
+contain the strings 'UTF-8' or 'UTF8' (case-insensitive matching),
+the default encoding of your STDIN, STDOUT, and STDERR, and of
+B<any subsequent file open>, is UTF-8.
+
+=item *
+
+Perl tries really hard to work both with Unicode and the old byte
+oriented world: most often this is nice, but sometimes this causes
+problems.
+
+=back
+
=head2 Using Unicode in XS
If you want to handle Perl Unicode in XS extensions, you may find
=item *
-DO_UTF8(sv) returns true if the UTF8 flag is on and the bytes
-pragma is not in effect. SvUTF8(sv) returns true is the UTF8
-flag is on, the bytes pragma is ignored. Remember that UTF8
-flag being on does not mean that there would be any characters
-of code points greater than 255 or 127 in the scalar, or that
-there even are any characters in the scalar. The UTF8 flag
-means that any characters added to the string will be encoded
-in UTF8 if the code points of the characters are greater than
-255. Not "if greater than 127", since Perl's Unicode model
-is not to use UTF-8 until it's really necessary.
+DO_UTF8(sv) returns true if the UTF8 flag is on and the bytes pragma
+is not in effect. SvUTF8(sv) returns true is the UTF8 flag is on, the
+bytes pragma is ignored. The UTF8 flag being on does B<not> mean that
+there are any characters of code points greater than 255 (or 127) in
+the scalar, or that there even are any characters in the scalar.
+What the UTF8 flag means is that the sequence of octets in the
+representation of the scalar is the sequence of UTF-8 encoded
+code points of the characters of a string. The UTF8 flag being
+off means that each octet in this representation encodes a single
+character with codepoint 0..255 within the string. Perl's Unicode
+model is not to use UTF-8 until it's really necessary.
=item *
encoded form. sv_utf8_downgrade(sv) does the opposite (if possible).
sv_utf8_encode(sv) is like sv_utf8_upgrade but the UTF8 flag does not
get turned on. sv_utf8_decode() does the opposite of sv_utf8_encode().
+Note that none of these are to be used as general purpose encoding/decoding
+interfaces: use Encode for that. sv_utf8_upgrade() is affected by the
+encoding pragma, but sv_utf8_downgrade() is not (since the encoding
+pragma is designed to be a one-way street).
=item *
For more information, see L<perlapi>, and F<utf8.c> and F<utf8.h>
in the Perl source code distribution.
+=head1 BUGS
+
+=head2 Interaction with locales
+
+Use of locales with Unicode data may lead to odd results. Currently
+there is some attempt to apply 8-bit locale info to characters in the
+range 0..255, but this is demonstrably incorrect for locales that use
+characters above that range when mapped into Unicode. It will also
+tend to run slower. Use of locales with Unicode is discouraged.
+
+=head2 Interaction with extensions
+
+When perl exchanges data with an extension, the extension should be
+able to understand the UTF-8 flag and act accordingly. If the
+extension doesn't know about the flag, the risk is high that it will
+return data that are incorrectly flagged.
+
+So if you're working with Unicode data, consult the documentation of
+every module you're using if there are any issues with Unicode data
+exchange. If the documentation does not talk about Unicode at all,
+suspect the worst and probably look at the source to learn how the
+module is implemented. Modules written completely in perl shouldn't
+cause problems. Modules that directly or indirectly access code written
+in other programming languages are at risk.
+
+For affected functions the simple strategy to avoid data corruption is
+to always make the encoding of the exchanged data explicit. Choose an
+encoding you know the extension can handle. Convert arguments passed
+to the extensions to that encoding and convert results back from that
+encoding. Write wrapper functions that do the conversions for you, so
+you can later change the functions when the extension catches up.
+
+To provide an example let's say the popular Foo::Bar::escape_html
+function doesn't deal with Unicode data yet. The wrapper function
+would convert the argument to raw UTF-8 and convert the result back to
+perl's internal representation like so:
+
+ sub my_escape_html ($) {
+ my($what) = shift;
+ return unless defined $what;
+ Encode::decode_utf8(Foo::Bar::escape_html(Encode::encode_utf8($what)));
+ }
+
+Sometimes, when the extension does not convert data but just stores
+and retrieves them, you will be in a position to use the otherwise
+dangerous Encode::_utf8_on() function. Let's say the popular
+C<Foo::Bar> extension, written in C, provides a C<param> method that
+lets you store and retrieve data according to these prototypes:
+
+ $self->param($name, $value); # set a scalar
+ $value = $self->param($name); # retrieve a scalar
+
+If it does not yet provide support for any encoding, one could write a
+derived class with such a C<param> method:
+
+ sub param {
+ my($self,$name,$value) = @_;
+ utf8::upgrade($name); # make sure it is UTF-8 encoded
+ if (defined $value)
+ utf8::upgrade($value); # make sure it is UTF-8 encoded
+ return $self->SUPER::param($name,$value);
+ } else {
+ my $ret = $self->SUPER::param($name);
+ Encode::_utf8_on($ret); # we know, it is UTF-8 encoded
+ return $ret;
+ }
+ }
+
+Some extensions provide filters on data entry/exit points, such as
+DB_File::filter_store_key and family. Look out for such filters in
+the documentation of your extensions, they can make the transition to
+Unicode data much easier.
+
+=head2 speed
+
+Some functions are slower when working on UTF-8 encoded strings than
+on byte encoded strings. All functions that need to hop over
+characters such as length(), substr() or index() can work B<much>
+faster when the underlying data are byte-encoded. Witness the
+following benchmark:
+
+ % perl -e '
+ use Benchmark;
+ use strict;
+ our $l = 10000;
+ our $u = our $b = "x" x $l;
+ substr($u,0,1) = "\x{100}";
+ timethese(-2,{
+ LENGTH_B => q{ length($b) },
+ LENGTH_U => q{ length($u) },
+ SUBSTR_B => q{ substr($b, $l/4, $l/2) },
+ SUBSTR_U => q{ substr($u, $l/4, $l/2) },
+ });
+ '
+ Benchmark: running LENGTH_B, LENGTH_U, SUBSTR_B, SUBSTR_U for at least 2 CPU seconds...
+ LENGTH_B: 2 wallclock secs ( 2.36 usr + 0.00 sys = 2.36 CPU) @ 5649983.05/s (n=13333960)
+ LENGTH_U: 2 wallclock secs ( 2.11 usr + 0.00 sys = 2.11 CPU) @ 12155.45/s (n=25648)
+ SUBSTR_B: 3 wallclock secs ( 2.16 usr + 0.00 sys = 2.16 CPU) @ 374480.09/s (n=808877)
+ SUBSTR_U: 2 wallclock secs ( 2.11 usr + 0.00 sys = 2.11 CPU) @ 6791.00/s (n=14329)
+
+The numbers show an incredible slowness on long UTF-8 strings and you
+should carefully avoid to use these functions within tight loops. For
+example if you want to iterate over characters, it is infinitely
+better to split into an array than to use substr, as the following
+benchmark shows:
+
+ % perl -e '
+ use Benchmark;
+ use strict;
+ our $l = 10000;
+ our $u = our $b = "x" x $l;
+ substr($u,0,1) = "\x{100}";
+ timethese(-5,{
+ SPLIT_B => q{ for my $c (split //, $b){} },
+ SPLIT_U => q{ for my $c (split //, $u){} },
+ SUBSTR_B => q{ for my $i (0..length($b)-1){my $c = substr($b,$i,1);} },
+ SUBSTR_U => q{ for my $i (0..length($u)-1){my $c = substr($u,$i,1);} },
+ });
+ '
+ Benchmark: running SPLIT_B, SPLIT_U, SUBSTR_B, SUBSTR_U for at least 5 CPU seconds...
+ SPLIT_B: 6 wallclock secs ( 5.29 usr + 0.00 sys = 5.29 CPU) @ 56.14/s (n=297)
+ SPLIT_U: 5 wallclock secs ( 5.17 usr + 0.01 sys = 5.18 CPU) @ 55.21/s (n=286)
+ SUBSTR_B: 5 wallclock secs ( 5.34 usr + 0.00 sys = 5.34 CPU) @ 123.22/s (n=658)
+ SUBSTR_U: 7 wallclock secs ( 6.20 usr + 0.00 sys = 6.20 CPU) @ 0.81/s (n=5)
+
+You see, the algorithm based on substr() was faster with byte encoded
+data but it is pathologically slow with UTF-8 data.
+
=head1 SEE ALSO
L<perluniintro>, L<encoding>, L<Encode>, L<open>, L<utf8>, L<bytes>,
https://perl5.git.perl.org / perl5.git / blobdiff