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Fix multicharacter titlecase (ucfirst).
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1=head1 NAME
2
3perlunicode - Unicode support in Perl
4
5=head1 DESCRIPTION
6
0a1f2d14 7=head2 Important Caveats
21bad921 8
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9WARNING: While the implementation of Unicode support in Perl is now
10fairly complete it is still evolving to some extent.
21bad921 11
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12In particular the way Unicode is handled on EBCDIC platforms is still
13rather experimental. On such a platform references to UTF-8 encoding
14in this document and elsewhere should be read as meaning UTF-EBCDIC as
15specified in Unicode Technical Report 16 unless ASCII vs EBCDIC issues
16are specifically discussed. There is no C<utfebcdic> pragma or
17":utfebcdic" layer, rather "utf8" and ":utf8" are re-used to mean
18platform's "natural" 8-bit encoding of Unicode. See L<perlebcdic> for
19more discussion of the issues.
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20
21The following areas are still under development.
21bad921 22
13a2d996 23=over 4
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24
25=item Input and Output Disciplines
26
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27A filehandle can be marked as containing perl's internal Unicode
28encoding (UTF-8 or UTF-EBCDIC) by opening it with the ":utf8" layer.
0a1f2d14 29Other encodings can be converted to perl's encoding on input, or from
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30perl's encoding on output by use of the ":encoding()" layer. There is
31not yet a clean way to mark the Perl source itself as being in an
32particular encoding.
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33
34=item Regular Expressions
35
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36The regular expression compiler does now attempt to produce
37polymorphic opcodes. That is the pattern should now adapt to the data
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38and automatically switch to the Unicode character scheme when
39presented with Unicode data, or a traditional byte scheme when
40presented with byte data. The implementation is still new and
41(particularly on EBCDIC platforms) may need further work.
21bad921 42
ad0029c4 43=item C<use utf8> still needed to enable UTF-8/UTF-EBCDIC in scripts
21bad921 44
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45The C<utf8> pragma implements the tables used for Unicode support.
46These tables are automatically loaded on demand, so the C<utf8> pragma
47need not normally be used.
21bad921 48
75daf61c 49However, as a compatibility measure, this pragma must be explicitly
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50used to enable recognition of UTF-8 in the Perl scripts themselves on
51ASCII based machines or recognize UTF-EBCDIC on EBCDIC based machines.
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52B<NOTE: this should be the only place where an explicit C<use utf8> is
53needed>.
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54
55=back
56
57=head2 Byte and Character semantics
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58
59Beginning with version 5.6, Perl uses logically wide characters to
60represent strings internally. This internal representation of strings
b3419ed8 61uses either the UTF-8 or the UTF-EBCDIC encoding.
393fec97 62
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63In future, Perl-level operations can be expected to work with
64characters rather than bytes, in general.
393fec97 65
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66However, as strictly an interim compatibility measure, Perl aims to
67provide a safe migration path from byte semantics to character
68semantics for programs. For operations where Perl can unambiguously
69decide that the input data is characters, Perl now switches to
70character semantics. For operations where this determination cannot
71be made without additional information from the user, Perl decides in
72favor of compatibility, and chooses to use byte semantics.
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73
74This behavior preserves compatibility with earlier versions of Perl,
75which allowed byte semantics in Perl operations, but only as long as
76none of the program's inputs are marked as being as source of Unicode
77character data. Such data may come from filehandles, from calls to
78external programs, from information provided by the system (such as %ENV),
21bad921 79or from literals and constants in the source text.
8cbd9a7a 80
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81If the C<-C> command line switch is used, (or the
82${^WIDE_SYSTEM_CALLS} global flag is set to C<1>), all system calls
83will use the corresponding wide character APIs. Note that this is
84currently only implemented on Windows since other platforms API
85standard on this area.
8cbd9a7a 86
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87Regardless of the above, the C<bytes> pragma can always be used to
88force byte semantics in a particular lexical scope. See L<bytes>.
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89
90The C<utf8> pragma is primarily a compatibility device that enables
75daf61c 91recognition of UTF-(8|EBCDIC) in literals encountered by the parser.
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92Note that this pragma is only required until a future version of Perl
93in which character semantics will become the default. This pragma may
94then become a no-op. See L<utf8>.
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95
96Unless mentioned otherwise, Perl operators will use character semantics
97when they are dealing with Unicode data, and byte semantics otherwise.
98Thus, character semantics for these operations apply transparently; if
99the input data came from a Unicode source (for example, by adding a
100character encoding discipline to the filehandle whence it came, or a
101literal UTF-8 string constant in the program), character semantics
102apply; otherwise, byte semantics are in effect. To force byte semantics
8058d7ab 103on Unicode data, the C<bytes> pragma should be used.
393fec97 104
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105Notice that if you have a string with byte semantics and you then
106add character data into it, the bytes will be upgraded I<as if they
107were ISO 8859-1 (Latin-1)> (or if in EBCDIC, after a translation
108to ISO 8859-1).
109
393fec97 110Under character semantics, many operations that formerly operated on
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111bytes change to operating on characters. For ASCII data this makes no
112difference, because UTF-8 stores ASCII in single bytes, but for any
113character greater than C<chr(127)>, the character B<may> be stored in
393fec97 114a sequence of two or more bytes, all of which have the high bit set.
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115
116For C1 controls or Latin 1 characters on an EBCDIC platform the
117character may be stored in a UTF-EBCDIC multi byte sequence. But by
118and large, the user need not worry about this, because Perl hides it
119from the user. A character in Perl is logically just a number ranging
120from 0 to 2**32 or so. Larger characters encode to longer sequences
121of bytes internally, but again, this is just an internal detail which
122is hidden at the Perl level.
393fec97 123
8cbd9a7a 124=head2 Effects of character semantics
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125
126Character semantics have the following effects:
127
128=over 4
129
130=item *
131
132Strings and patterns may contain characters that have an ordinal value
21bad921 133larger than 255.
393fec97 134
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135Presuming you use a Unicode editor to edit your program, such
136characters will typically occur directly within the literal strings as
137UTF-8 (or UTF-EBCDIC on EBCDIC platforms) characters, but you can also
138specify a particular character with an extension of the C<\x>
139notation. UTF-X characters are specified by putting the hexadecimal
140code within curlies after the C<\x>. For instance, a Unicode smiley
141face is C<\x{263A}>.
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142
143=item *
144
145Identifiers within the Perl script may contain Unicode alphanumeric
146characters, including ideographs. (You are currently on your own when
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147it comes to using the canonical forms of characters--Perl doesn't
148(yet) attempt to canonicalize variable names for you.)
393fec97 149
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150=item *
151
152Regular expressions match characters instead of bytes. For instance,
153"." matches a character instead of a byte. (However, the C<\C> pattern
75daf61c 154is provided to force a match a single byte ("C<char>" in C, hence C<\C>).)
393fec97 155
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156=item *
157
158Character classes in regular expressions match characters instead of
159bytes, and match against the character properties specified in the
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160Unicode properties database. So C<\w> can be used to match an
161ideograph, for instance.
393fec97 162
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163=item *
164
165Named Unicode properties and block ranges make be used as character
166classes via the new C<\p{}> (matches property) and C<\P{}> (doesn't
167match property) constructs. For instance, C<\p{Lu}> matches any
168character with the Unicode uppercase property, while C<\p{M}> matches
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169any mark character. Single letter properties may omit the brackets,
170so that can be written C<\pM> also. Many predefined character classes
a1cc1cb1 171are available, such as C<\p{IsMirrored}> and C<\p{InTibetan}>.
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172
173The C<\p{Is...}> test for "general properties" such as "letter",
174"digit", while the C<\p{In...}> test for Unicode scripts and blocks.
175
176The official Unicode script and block names have spaces and
177dashes and separators, but for convenience you can have
178dashes, spaces, and underbars at every word division, and
179you need not care about correct casing. It is recommended,
180however, that for consistency you use the following naming:
181the official Unicode script or block name (see below for
182the additional rules that apply to block names), with the whitespace
183and dashes removed, and the words "uppercase-first-lowercase-otherwise".
184That is, "Latin-1 Supplement" becomes "Latin1Supplement".
185
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186You can also negate both C<\p{}> and C<\P{}> by introducing a caret
187(^) between the first curly and the property name: C<\p{^InTamil}> is
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188equal to C<\P{InTamil}>.
189
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190The C<In> and C<Is> can be left out: C<\p{Greek}> is equal to
191C<\p{InGreek}>, C<\P{Pd}> is equal to C<\P{Pd}>.
393fec97 192
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193 Short Long
194
195 L Letter
196 Lu Uppercase Letter
197 Ll Lowercase Letter
198 Lt Titlecase Letter
199 Lm Modifier Letter
200 Lo Other Letter
201
202 M Mark
203 Mn Non-Spacing Mark
204 Mc Spacing Combining Mark
205 Me Enclosing Mark
206
207 N Number
208 Nd Decimal Digit Number
209 Nl Letter Number
210 No Other Number
211
212 P Punctuation
213 Pc Connector Punctuation
214 Pd Dash Punctuation
215 Ps Open Punctuation
216 Pe Close Punctuation
217 Pi Initial Punctuation
218 (may behave like Ps or Pe depending on usage)
219 Pf Final Punctuation
220 (may behave like Ps or Pe depending on usage)
221 Po Other Punctuation
222
223 S Symbol
224 Sm Math Symbol
225 Sc Currency Symbol
226 Sk Modifier Symbol
227 So Other Symbol
228
229 Z Separator
230 Zs Space Separator
231 Zl Line Separator
232 Zp Paragraph Separator
233
234 C Other
235 Cc (Other) Control
236 Cf (Other) Format
237 Cs (Other) Surrogate
238 Co (Other) Private Use
239 Cn (Other) Not Assigned
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240
241There's also C<L&> which is an alias for C<Ll>, C<Lu>, and C<Lt>.
32293815 242
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243The following reserved ranges have C<In> tests:
244
245 CJK Ideograph Extension A
246 CJK Ideograph
247 Hangul Syllable
248 Non Private Use High Surrogate
249 Private Use High Surrogate
250 Low Surrogate
251 Private Surrogate
252 CJK Ideograph Extension B
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253 Plane 15 Private Use
254 Plane 16 Private Use
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255
256For example C<"\x{AC00}" =~ \p{HangulSyllable}> will test true.
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257(Handling of surrogates is not implemented yet, because Perl
258uses UTF-8 and not UTF-16 internally to represent Unicode.)
d73e5302 259
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260Additionally, because scripts differ in their directionality
261(for example Hebrew is written right to left), all characters
262have their directionality defined:
263
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264 BidiL Left-to-Right
265 BidiLRE Left-to-Right Embedding
266 BidiLRO Left-to-Right Override
267 BidiR Right-to-Left
268 BidiAL Right-to-Left Arabic
269 BidiRLE Right-to-Left Embedding
270 BidiRLO Right-to-Left Override
271 BidiPDF Pop Directional Format
272 BidiEN European Number
273 BidiES European Number Separator
274 BidiET European Number Terminator
275 BidiAN Arabic Number
276 BidiCS Common Number Separator
277 BidiNSM Non-Spacing Mark
278 BidiBN Boundary Neutral
279 BidiB Paragraph Separator
280 BidiS Segment Separator
281 BidiWS Whitespace
282 BidiON Other Neutrals
32293815 283
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284=head2 Scripts
285
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286The scripts available for C<\p{In...}> and C<\P{In...}>, for example
287\p{InCyrillic>, are as follows, for example C<\p{InLatin}> or C<\P{InHan}>:
2796c109 288
1ac13f9a 289 Arabic
e9ad1727 290 Armenian
1ac13f9a 291 Bengali
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292 Bopomofo
293 Canadian-Aboriginal
294 Cherokee
295 Cyrillic
296 Deseret
297 Devanagari
298 Ethiopic
299 Georgian
300 Gothic
301 Greek
1ac13f9a 302 Gujarati
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303 Gurmukhi
304 Han
305 Hangul
306 Hebrew
307 Hiragana
308 Inherited
1ac13f9a 309 Kannada
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310 Katakana
311 Khmer
1ac13f9a 312 Lao
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313 Latin
314 Malayalam
315 Mongolian
1ac13f9a 316 Myanmar
1ac13f9a 317 Ogham
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318 Old-Italic
319 Oriya
1ac13f9a 320 Runic
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321 Sinhala
322 Syriac
323 Tamil
324 Telugu
325 Thaana
326 Thai
327 Tibetan
1ac13f9a 328 Yi
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329
330There are also extended property classes that supplement the basic
331properties, defined by the F<PropList> Unicode database:
332
e9ad1727 333 ASCII_Hex_Digit
1ac13f9a 334 Bidi_Control
1ac13f9a 335 Dash
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336 Diacritic
337 Extender
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338 Hex_Digit
339 Hyphen
340 Ideographic
341 Join_Control
342 Noncharacter_Code_Point
343 Other_Alphabetic
1ac13f9a 344 Other_Lowercase
e9ad1727 345 Other_Math
1ac13f9a 346 Other_Uppercase
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347 Quotation_Mark
348 White_space
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349
350and further derived properties:
351
352 Alphabetic Lu + Ll + Lt + Lm + Lo + Other_Alphabetic
353 Lowercase Ll + Other_Lowercase
354 Uppercase Lu + Other_Uppercase
355 Math Sm + Other_Math
356
357 ID_Start Lu + Ll + Lt + Lm + Lo + Nl
358 ID_Continue ID_Start + Mn + Mc + Nd + Pc
359
360 Any Any character
361 Assigned Any non-Cn character
362 Common Any character (or unassigned code point)
363 not explicitly assigned to a script.
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364
365=head2 Blocks
366
367In addition to B<scripts>, Unicode also defines B<blocks> of
368characters. The difference between scripts and blocks is that the
e9ad1727 369scripts concept is closer to natural languages, while the blocks
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370concept is more an artificial grouping based on groups of 256 Unicode
371characters. For example, the C<Latin> script contains letters from
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372many blocks. On the other hand, the C<Latin> script does not contain
373all the characters from those blocks, it does not for example contain
374digits because digits are shared across many scripts. Digits and
375other similar groups, like punctuation, are in a category called
376C<Common>.
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377
378For more about scripts see the UTR #24:
379http://www.unicode.org/unicode/reports/tr24/
380For more about blocks see
381http://www.unicode.org/Public/UNIDATA/Blocks.txt
382
383Because there are overlaps in naming (there are, for example, both
384a script called C<Katakana> and a block called C<Katakana>, the block
385version has C<Block> appended to its name, C<\p{InKatakanaBlock}>.
386
387Notice that this definition was introduced in Perl 5.8.0: in Perl
3885.6.0 only the blocks were used; in Perl 5.8.0 scripts became the
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389preferential Unicode character class definition; this meant that
390the definitions of some character classes changed (the ones in the
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391below list that have the C<Block> appended).
392
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393 Alphabetic Presentation Forms
394 Arabic Block
395 Arabic Presentation Forms-A
396 Arabic Presentation Forms-B
397 Armenian Block
398 Arrows
71d929cb 399 Basic Latin
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400 Bengali Block
401 Block Elements
402 Bopomofo Block
403 Bopomofo Extended
404 Box Drawing
405 Braille Patterns
406 Byzantine Musical Symbols
407 CJK Compatibility
408 CJK Compatibility Forms
409 CJK Compatibility Ideographs
410 CJK Compatibility Ideographs Supplement
411 CJK Radicals Supplement
412 CJK Symbols and Punctuation
413 CJK Unified Ideographs
414 CJK Unified Ideographs Extension A
415 CJK Unified Ideographs Extension B
416 Cherokee Block
71d929cb 417 Combining Diacritical Marks
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418 Combining Half Marks
419 Combining Marks for Symbols
420 Control Pictures
421 Currency Symbols
71d929cb 422 Cyrillic Block
e9ad1727 423 Deseret Block
71d929cb 424 Devanagari Block
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425 Dingbats
426 Enclosed Alphanumerics
427 Enclosed CJK Letters and Months
428 Ethiopic Block
429 General Punctuation
430 Geometric Shapes
71d929cb 431 Georgian Block
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432 Gothic Block
433 Greek Block
434 Greek Extended
435 Gujarati Block
436 Gurmukhi Block
437 Halfwidth and Fullwidth Forms
438 Hangul Compatibility Jamo
71d929cb 439 Hangul Jamo
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440 Hangul Syllables
441 Hebrew Block
442 High Private Use Surrogates
443 High Surrogates
444 Hiragana Block
445 IPA Extensions
446 Ideographic Description Characters
447 Kanbun
448 Kangxi Radicals
449 Kannada Block
450 Katakana Block
71d929cb 451 Khmer Block
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452 Lao Block
453 Latin 1 Supplement
71d929cb 454 Latin Extended Additional
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455 Latin Extended-A
456 Latin Extended-B
71d929cb 457 Letterlike Symbols
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458 Low Surrogates
459 Malayalam Block
460 Mathematical Alphanumeric Symbols
71d929cb 461 Mathematical Operators
e9ad1727 462 Miscellaneous Symbols
71d929cb 463 Miscellaneous Technical
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464 Mongolian Block
465 Musical Symbols
466 Myanmar Block
467 Number Forms
468 Ogham Block
469 Old Italic Block
71d929cb 470 Optical Character Recognition
e9ad1727 471 Oriya Block
71d929cb 472 Private Use
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473 Runic Block
474 Sinhala Block
71d929cb 475 Small Form Variants
e9ad1727 476 Spacing Modifier Letters
2796c109 477 Specials
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478 Superscripts and Subscripts
479 Syriac Block
2796c109 480 Tags
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481 Tamil Block
482 Telugu Block
483 Thaana Block
484 Thai Block
485 Tibetan Block
486 Unified Canadian Aboriginal Syllabics
487 Yi Radicals
488 Yi Syllables
32293815 489
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490=item *
491
492The special pattern C<\X> match matches any extended Unicode sequence
493(a "combining character sequence" in Standardese), where the first
494character is a base character and subsequent characters are mark
495characters that apply to the base character. It is equivalent to
496C<(?:\PM\pM*)>.
497
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498=item *
499
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500The C<tr///> operator translates characters instead of bytes. Note
501that the C<tr///CU> functionality has been removed, as the interface
502was a mistake. For similar functionality see pack('U0', ...) and
503pack('C0', ...).
393fec97 504
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505=item *
506
507Case translation operators use the Unicode case translation tables
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508when provided character input. Note that C<uc()> (also known as C<\U>
509in doublequoted strings) translates to uppercase, while C<ucfirst>
510(also known as C<\u> in doublequoted strings) translates to titlecase
511(for languages that make the distinction). Naturally the
512corresponding backslash sequences have the same semantics.
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513
514=item *
515
516Most operators that deal with positions or lengths in the string will
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517automatically switch to using character positions, including
518C<chop()>, C<substr()>, C<pos()>, C<index()>, C<rindex()>,
519C<sprintf()>, C<write()>, and C<length()>. Operators that
520specifically don't switch include C<vec()>, C<pack()>, and
521C<unpack()>. Operators that really don't care include C<chomp()>, as
522well as any other operator that treats a string as a bucket of bits,
523such as C<sort()>, and the operators dealing with filenames.
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524
525=item *
526
527The C<pack()>/C<unpack()> letters "C<c>" and "C<C>" do I<not> change,
528since they're often used for byte-oriented formats. (Again, think
529"C<char>" in the C language.) However, there is a new "C<U>" specifier
530that will convert between UTF-8 characters and integers. (It works
531outside of the utf8 pragma too.)
532
533=item *
534
535The C<chr()> and C<ord()> functions work on characters. This is like
536C<pack("U")> and C<unpack("U")>, not like C<pack("C")> and
537C<unpack("C")>. In fact, the latter are how you now emulate
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538byte-oriented C<chr()> and C<ord()> for Unicode strings.
539(Note that this reveals the internal UTF-8 encoding of strings and
540you are not supposed to do that unless you know what you are doing.)
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541
542=item *
543
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544The bit string operators C<& | ^ ~> can operate on character data.
545However, for backward compatibility reasons (bit string operations
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546when the characters all are less than 256 in ordinal value) one should
547not mix C<~> (the bit complement) and characters both less than 256 and
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548equal or greater than 256. Most importantly, the DeMorgan's laws
549(C<~($x|$y) eq ~$x&~$y>, C<~($x&$y) eq ~$x|~$y>) won't hold.
550Another way to look at this is that the complement cannot return
75daf61c 551B<both> the 8-bit (byte) wide bit complement B<and> the full character
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552wide bit complement.
553
554=item *
555
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556lc(), uc(), lcfirst(), and ucfirst() work for the following cases:
557
558=over 8
559
560=item *
561
562the case mapping is from a single Unicode character to another
563single Unicode character
564
565=item *
566
567the case mapping is from a single Unicode character to more
568than one Unicode character
569
570=back
571
572What doesn't yet work are the followng cases:
573
574=over 8
575
576=item *
577
578the "final sigma" (Greek)
579
580=item *
581
582anything to with locales (Lithuanian, Turkish, Azeri)
583
584=back
585
586See the Unicode Technical Report #21, Case Mappings, for more details.
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587
588=item *
589
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590And finally, C<scalar reverse()> reverses by character rather than by byte.
591
592=back
593
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594=head2 Character encodings for input and output
595
7221edc9 596See L<Encode>.
8cbd9a7a 597
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598=head1 CAVEATS
599
600As of yet, there is no method for automatically coercing input and
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601output to some encoding other than UTF-8 or UTF-EBCDIC. This is planned
602in the near future, however.
393fec97 603
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604Whether an arbitrary piece of data will be treated as "characters" or
605"bytes" by internal operations cannot be divined at the current time.
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606
607Use of locales with utf8 may lead to odd results. Currently there is
608some attempt to apply 8-bit locale info to characters in the range
6090..255, but this is demonstrably incorrect for locales that use
610characters above that range (when mapped into Unicode). It will also
611tend to run slower. Avoidance of locales is strongly encouraged.
612
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613=head1 UNICODE REGULAR EXPRESSION SUPPORT LEVEL
614
615The following list of Unicode regular expression support describes
616feature by feature the Unicode support implemented in Perl as of Perl
6175.8.0. The "Level N" and the section numbers refer to the Unicode
618Technical Report 18, "Unicode Regular Expression Guidelines".
619
620=over 4
621
622=item *
623
624Level 1 - Basic Unicode Support
625
626 2.1 Hex Notation - done [1]
627 Named Notation - done [2]
628 2.2 Categories - done [3][4]
629 2.3 Subtraction - MISSING [5][6]
630 2.4 Simple Word Boundaries - done [7]
631 2.5 Simple Loose Matches - MISSING [8]
632 2.6 End of Line - MISSING [9][10]
633
634 [ 1] \x{...}
635 [ 2] \N{...}
636 [ 3] . \p{Is...} \P{Is...}
637 [ 4] now scripts (see UTR#24 Script Names) in addition to blocks
638 [ 5] have negation
639 [ 6] can use look-ahead to emulate subtracion
640 [ 7] include Letters in word characters
641 [ 8] see UTR#21 Case Mappings
642 [ 9] see UTR#13 Unicode Newline Guidelines
643 [10] should do ^ and $ also on \x{2028} and \x{2029}
644
645=item *
646
647Level 2 - Extended Unicode Support
648
649 3.1 Surrogates - MISSING
650 3.2 Canonical Equivalents - MISSING [11][12]
651 3.3 Locale-Independent Graphemes - MISSING [13]
652 3.4 Locale-Independent Words - MISSING [14]
653 3.5 Locale-Independent Loose Matches - MISSING [15]
654
655 [11] see UTR#15 Unicode Normalization
656 [12] have Unicode::Normalize but not integrated to regexes
657 [13] have \X but at this level . should equal that
658 [14] need three classes, not just \w and \W
659 [15] see UTR#21 Case Mappings
660
661=item *
662
663Level 3 - Locale-Sensitive Support
664
665 4.1 Locale-Dependent Categories - MISSING
666 4.2 Locale-Dependent Graphemes - MISSING [16][17]
667 4.3 Locale-Dependent Words - MISSING
668 4.4 Locale-Dependent Loose Matches - MISSING
669 4.5 Locale-Dependent Ranges - MISSING
670
671 [16] see UTR#10 Unicode Collation Algorithms
672 [17] have Unicode::Collate but not integrated to regexes
673
674=back
675
393fec97
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676=head1 SEE ALSO
677
32293815 678L<bytes>, L<utf8>, L<perlretut>, L<perlvar/"${^WIDE_SYSTEM_CALLS}">
393fec97
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679
680=cut