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PERLUNIINTRO(1) 		 Perl Programmers Reference Guide		  PERLUNIINTRO(1)

       perluniintro - Perl Unicode introduction

       This document gives a general idea of Unicode and how to use Unicode in Perl.


       Unicode is a character set standard which plans to codify all of the writing systems of
       the world, plus many other symbols.

       Unicode and ISO/IEC 10646 are coordinated standards that provide code points for charac-
       ters in almost all modern character set standards, covering more than 30 writing systems
       and hundreds of languages, including all commercially-important modern languages.  All
       characters in the largest Chinese, Japanese, and Korean dictionaries are also encoded. The
       standards will eventually cover almost all characters in more than 250 writing systems and
       thousands of languages.

       A Unicode character is an abstract entity.  It is not bound to any particular integer
       width, especially not to the C language "char".	Unicode is language-neutral and dis-
       play-neutral: it does not encode the language of the text and it does not define fonts or
       other graphical layout details.	Unicode operates on characters and on text built from
       those characters.

       Unicode defines characters like "LATIN CAPITAL LETTER A" or "GREEK SMALL LETTER ALPHA" and
       unique numbers for the characters, in this case 0x0041 and 0x03B1, respectively.  These
       unique numbers are called code points.

       The Unicode standard prefers using hexadecimal notation for the code points.  If numbers
       like 0x0041 are unfamiliar to you, take a peek at a later section, "Hexadecimal Notation".
       The Unicode standard uses the notation "U+0041 LATIN CAPITAL LETTER A", to give the hexa-
       decimal code point and the normative name of the character.

       Unicode also defines various properties for the characters, like "uppercase" or "lower-
       case", "decimal digit", or "punctuation"; these properties are independent of the names of
       the characters.	Furthermore, various operations on the characters like uppercasing, low-
       ercasing, and collating (sorting) are defined.

       A Unicode character consists either of a single code point, or a base character (like
       "LATIN CAPITAL LETTER A"), followed by one or more modifiers (like "COMBINING ACUTE
       ACCENT").  This sequence of base character and modifiers is called a combining character

       Whether to call these combining character sequences "characters" depends on your point of
       view. If you are a programmer, you probably would tend towards seeing each element in the
       sequences as one unit, or "character".  The whole sequence could be seen as one "charac-
       ter", however, from the user's point of view, since that's probably what it looks like in
       the context of the user's language.

       With this "whole sequence" view of characters, the total number of characters is
       open-ended. But in the programmer's "one unit is one character" point of view, the concept
       of "characters" is more deterministic.  In this document, we take that second  point of
       view: one "character" is one Unicode code point, be it a base character or a combining

       For some combinations, there are precomposed characters.  "LATIN CAPITAL LETTER A WITH
       ACUTE", for example, is defined as a single code point.	These precomposed characters are,
       however, only available for some combinations, and are mainly meant to support round-trip
       conversions between Unicode and legacy standards (like the ISO 8859).  In the general
       case, the composing method is more extensible.  To support conversion between different
       compositions of the characters, various normalization forms to standardize representations
       are also defined.

       Because of backward compatibility with legacy encodings, the "a unique number for every
       character" idea breaks down a bit: instead, there is "at least one number for every char-
       acter".	The same character could be represented differently in several legacy encodings.
       The converse is also not true: some code points do not have an assigned character.
       Firstly, there are unallocated code points within otherwise used blocks.  Secondly, there
       are special Unicode control characters that do not represent true characters.

       A common myth about Unicode is that it would be "16-bit", that is, Unicode is only repre-
       sented as 0x10000 (or 65536) characters from 0x0000 to 0xFFFF.  This is untrue. Since Uni-
       code 2.0, Unicode has been defined all the way up to 21 bits(0x10FFFF), and since Unicode
       3.1, characters have been defined beyond 0xFFFF.  The first 0x10000 characters are called
       the Plane 0, or the Basic Multilingual Plane (BMP).  With Unicode 3.1, 17 planes in all
       are defined--but nowhere near full of defined characters, yet.

       Another myth is that the 256-character blocks have something to do with languages--that
       each block would define the characters used by a language or a set of languages.  This is
       also untrue.  The division into blocks exists, but it is almost completely accidental--an
       artifact of how the characters have been and still are allocated.  Instead, there is a
       concept called scripts, which is more useful: there is "Latin" script, "Greek" script, and
       so on.  Scripts usually span varied parts of several blocks.  For further information see

       The Unicode code points are just abstract numbers.  To input and output these abstract
       numbers, the numbers must be encoded somehow.  Unicode defines several character encoding
       forms, of which UTF-8 is perhaps the most popular.  UTF-8 is a variable length encoding
       that encodes Unicode characters as 1 to 6 bytes (only 4 with the currently defined charac-
       ters).  Other encodings include UTF-16 and UTF-32 and their big- and little-endian vari-
       ants (UTF-8 is byte-order independent) The ISO/IEC 10646 defines the UCS-2 and UCS-4
       encoding forms.

       For more information about encodings--for instance, to learn what surrogates and byte
       order marks (BOMs) are--see perlunicode.

       Perl's Unicode Support

       Starting from Perl 5.6.0, Perl has had the capacity to handle Unicode natively.	Perl
       5.8.0, however, is the first recommended release for serious Unicode work.  The mainte-
       nance release 5.6.1 fixed many of the problems of the initial Unicode implementation, but
       for example regular expressions still do not work with Unicode in 5.6.1.

       Starting from Perl 5.8.0, the use of "use utf8" is no longer necessary. In earlier
       releases the "utf8" pragma was used to declare that operations in the current block or
       file would be Unicode-aware.  This model was found to be wrong, or at least clumsy: the
       "Unicodeness" is now carried with the data, instead of being attached to the operations.
       Only one case remains where an explicit "use utf8" is needed: if your Perl script itself
       is encoded in UTF-8, you can use UTF-8 in your identifier names, and in string and regular
       expression literals, by saying "use utf8".  This is not the default because scripts with
       legacy 8-bit data in them would break.  See utf8.

       Perl's Unicode Model

       Perl supports both pre-5.6 strings of eight-bit native bytes, and strings of Unicode char-
       acters.	The principle is that Perl tries to keep its data as eight-bit bytes for as long
       as possible, but as soon as Unicodeness cannot be avoided, the data is transparently
       upgraded to Unicode.

       Internally, Perl currently uses either whatever the native eight-bit character set of the
       platform (for example Latin-1) is, defaulting to UTF-8, to encode Unicode strings. Specif-
       ically, if all code points in the string are 0xFF or less, Perl uses the native eight-bit
       character set.  Otherwise, it uses UTF-8.

       A user of Perl does not normally need to know nor care how Perl happens to encode its
       internal strings, but it becomes relevant when outputting Unicode strings to a stream
       without a PerlIO layer -- one with the "default" encoding.  In such a case, the raw bytes
       used internally (the native character set or UTF-8, as appropriate for each string) will
       be used, and a "Wide character" warning will be issued if those strings contain a charac-
       ter beyond 0x00FF.

       For example,

	     perl -e 'print "\x{DF}\n", "\x{0100}\x{DF}\n"'

       produces a fairly useless mixture of native bytes and UTF-8, as well as a warning:

	    Wide character in print at ...

       To output UTF-8, use the ":utf8" output layer.  Prepending

	     binmode(STDOUT, ":utf8");

       to this sample program ensures that the output is completely UTF-8, and removes the pro-
       gram's warning.

       If your locale environment variables ("LANGUAGE", "LC_ALL", "LC_CTYPE", "LANG") contain
       the strings 'UTF-8' or 'UTF8', regardless of case, then the default encoding of your
       STDIN, STDOUT, and STDERR and of any subsequent file open, is UTF-8.  Note that this means
       that Perl expects other software to work, too: if Perl has been led to believe that STDIN
       should be UTF-8, but then STDIN coming in from another command is not UTF-8, Perl will
       complain about the malformed UTF-8.

       All features that combine Unicode and I/O also require using the new PerlIO feature.
       Almost all Perl 5.8 platforms do use PerlIO, though: you can see whether yours is by run-
       ning "perl -V" and looking for "useperlio=define".

       Unicode and EBCDIC

       Perl 5.8.0 also supports Unicode on EBCDIC platforms.  There, Unicode support is somewhat
       more complex to implement since additional conversions are needed at every step.  Some
       problems remain, see perlebcdic for details.

       In any case, the Unicode support on EBCDIC platforms is better than in the 5.6 series,
       which didn't work much at all for EBCDIC platform.  On EBCDIC platforms, the internal Uni-
       code encoding form is UTF-EBCDIC instead of UTF-8.  The difference is that as UTF-8 is
       "ASCII-safe" in that ASCII characters encode to UTF-8 as-is, while UTF-EBCDIC is

       Creating Unicode

       To create Unicode characters in literals for code points above 0xFF, use the "\x{...}"
       notation in double-quoted strings:

	   my $smiley = "\x{263a}";

       Similarly, it can be used in regular expression literals

	   $smiley =~ /\x{263a}/;

       At run-time you can use "chr()":

	   my $hebrew_alef = chr(0x05d0);

       See "Further Resources" for how to find all these numeric codes.

       Naturally, "ord()" will do the reverse: it turns a character into a code point.

       Note that "\x.." (no "{}" and only two hexadecimal digits), "\x{...}", and "chr(...)" for
       arguments less than 0x100 (decimal 256) generate an eight-bit character for backward com-
       patibility with older Perls.  For arguments of 0x100 or more, Unicode characters are
       always produced. If you want to force the production of Unicode characters regardless of
       the numeric value, use "pack("U", ...)"	instead of "\x..", "\x{...}", or "chr()".

       You can also use the "charnames" pragma to invoke characters by name in double-quoted

	   use charnames ':full';
	   my $arabic_alef = "\N{ARABIC LETTER ALEF}";

       And, as mentioned above, you can also "pack()" numbers into Unicode characters:

	  my $georgian_an  = pack("U", 0x10a0);

       Note that both "\x{...}" and "\N{...}" are compile-time string constants: you cannot use
       variables in them.  if you want similar run-time functionality, use "chr()" and "char-

       Also note that if all the code points for pack "U" are below 0x100, bytes will be gener-
       ated, just like if you were using "chr()".

	  my $bytes = pack("U*", 0x80, 0xFF);

       If you want to force the result to Unicode characters, use the special "U0" prefix.  It
       consumes no arguments but forces the result to be in Unicode characters, instead of bytes.

	  my $chars = pack("U0U*", 0x80, 0xFF);

       Handling Unicode

       Handling Unicode is for the most part transparent: just use the strings as usual.  Func-
       tions like "index()", "length()", and "substr()" will work on the Unicode characters; reg-
       ular expressions will work on the Unicode characters (see perlunicode and perlretut).

       Note that Perl considers combining character sequences to be characters, so for example

	   use charnames ':full';

       will print 2, not 1.  The only exception is that regular expressions have "\X" for match-
       ing a combining character sequence.

       Life is not quite so transparent, however, when working with legacy encodings, I/O, and
       certain special cases:

       Legacy Encodings

       When you combine legacy data and Unicode the legacy data needs to be upgraded to Unicode.
       Normally ISO 8859-1 (or EBCDIC, if applicable) is assumed.  You can override this assump-
       tion by using the "encoding" pragma, for example

	   use encoding 'latin2'; # ISO 8859-2

       in which case literals (string or regular expressions), "chr()", and "ord()" in your whole
       script are assumed to produce Unicode characters from ISO 8859-2 code points.  Note that
       the matching for encoding names is forgiving: instead of "latin2" you could have said
       "Latin 2", or "iso8859-2", or other variations.	With just

	   use encoding;

       the environment variable "PERL_ENCODING" will be consulted.  If that variable isn't set,
       the encoding pragma will fail.

       The "Encode" module knows about many encodings and has interfaces for doing conversions
       between those encodings:

	   use Encode 'from_to';
	   from_to($data, "iso-8859-3", "utf-8"); # from legacy to utf-8

       Unicode I/O

       Normally, writing out Unicode data

	   print FH $some_string_with_unicode, "\n";

       produces raw bytes that Perl happens to use to internally encode the Unicode string.
       Perl's internal encoding depends on the system as well as what characters happen to be in
       the string at the time. If any of the characters are at code points 0x100 or above, you
       will get a warning.  To ensure that the output is explicitly rendered in the encoding you
       desire--and to avoid the warning--open the stream with the desired encoding. Some exam-

	   open FH, ">:utf8", "file";

	   open FH, ">:encoding(ucs2)",      "file";
	   open FH, ">:encoding(UTF-8)",     "file";
	   open FH, ">:encoding(shift_jis)", "file";

       and on already open streams, use "binmode()":

	   binmode(STDOUT, ":utf8");

	   binmode(STDOUT, ":encoding(ucs2)");
	   binmode(STDOUT, ":encoding(UTF-8)");
	   binmode(STDOUT, ":encoding(shift_jis)");

       The matching of encoding names is loose: case does not matter, and many encodings have
       several aliases.  Note that the ":utf8" layer must always be specified exactly like that;
       it is not subject to the loose matching of encoding names.

       See PerlIO for the ":utf8" layer, PerlIO::encoding and Encode::PerlIO for the ":encod-
       ing()" layer, and Encode::Supported for many encodings supported by the "Encode" module.

       Reading in a file that you know happens to be encoded in one of the Unicode or legacy
       encodings does not magically turn the data into Unicode in Perl's eyes.	To do that, spec-
       ify the appropriate layer when opening files

	   open(my $fh,'<:utf8', 'anything');
	   my $line_of_unicode = <$fh>;

	   open(my $fh,'<:encoding(Big5)', 'anything');
	   my $line_of_unicode = <$fh>;

       The I/O layers can also be specified more flexibly with the "open" pragma.  See open, or
       look at the following example.

	   use open ':utf8'; # input and output default layer will be UTF-8
	   open X, ">file";
	   print X chr(0x100), "\n";
	   close X;
	   open Y, "<file";
	   printf "%#x\n", ord(<Y>); # this should print 0x100
	   close Y;

       With the "open" pragma you can use the ":locale" layer

	   $ENV{LC_ALL} = $ENV{LANG} = 'ru_RU.KOI8-R';
	   # the :locale will probe the locale environment variables like LC_ALL
	   use open OUT => ':locale'; # russki parusski
	   open(O, ">koi8");
	   print O chr(0x430); # Unicode CYRILLIC SMALL LETTER A = KOI8-R 0xc1
	   close O;
	   open(I, "<koi8");
	   printf "%#x\n", ord(<I>), "\n"; # this should print 0xc1
	   close I;

       or you can also use the ':encoding(...)' layer

	   open(my $epic,'<:encoding(iso-8859-7)','iliad.greek');
	   my $line_of_unicode = <$epic>;

       These methods install a transparent filter on the I/O stream that converts data from the
       specified encoding when it is read in from the stream.  The result is always Unicode.

       The open pragma affects all the "open()" calls after the pragma by setting default layers.
       If you want to affect only certain streams, use explicit layers directly in the "open()"

       You can switch encodings on an already opened stream by using "binmode()"; see "binmode"
       in perlfunc.

       The ":locale" does not currently (as of Perl 5.8.0) work with "open()" and "binmode()",
       only with the "open" pragma.  The ":utf8" and ":encoding(...)" methods do work with all of
       "open()", "binmode()", and the "open" pragma.

       Similarly, you may use these I/O layers on output streams to automatically convert Unicode
       to the specified encoding when it is written to the stream. For example, the following
       snippet copies the contents of the file "text.jis" (encoded as ISO-2022-JP, aka JIS) to
       the file "text.utf8", encoded as UTF-8:

	   open(my $nihongo, '<:encoding(iso-2022-jp)', 'text.jis');
	   open(my $unicode, '>:utf8',			'text.utf8');
	   while (<$nihongo>) { print $unicode $_ }

       The naming of encodings, both by the "open()" and by the "open" pragma, is similar to the
       "encoding" pragma in that it allows for flexible names: "koi8-r" and "KOI8R" will both be

       Common encodings recognized by ISO, MIME, IANA, and various other standardisation organi-
       sations are recognised; for a more detailed list see Encode::Supported.

       "read()" reads characters and returns the number of characters.	"seek()" and "tell()"
       operate on byte counts, as do "sysread()" and "sysseek()".

       Notice that because of the default behaviour of not doing any conversion upon input if
       there is no default layer, it is easy to mistakenly write code that keeps on expanding a
       file by repeatedly encoding the data:

	   open F, "file";
	   local $/; ## read in the whole file of 8-bit characters
	   $t = <F>;
	   close F;
	   open F, ">:utf8", "file";
	   print F $t; ## convert to UTF-8 on output
	   close F;

       If you run this code twice, the contents of the file will be twice UTF-8 encoded.  A "use
       open ':utf8'" would have avoided the bug, or explicitly opening also the file for input as

       NOTE: the ":utf8" and ":encoding" features work only if your Perl has been built with the
       new PerlIO feature.

       Displaying Unicode As Text

       Sometimes you might want to display Perl scalars containing Unicode as simple ASCII (or
       EBCDIC) text.  The following subroutine converts its argument so that Unicode characters
       with code points greater than 255 are displayed as "\x{...}", control characters (like
       "\n") are displayed as "\x..", and the rest of the characters as themselves:

	  sub nice_string {
		map { $_ > 255 ?		  # if wide character...
		      sprintf("\\x{%04X}", $_) :  # \x{...}
		      chr($_) =~ /[[:cntrl:]]/ ?  # else if control character ...
		      sprintf("\\x%02X", $_) :	  # \x..
		      chr($_)			  # else as themselves
		} unpack("U*", $_[0])); 	  # unpack Unicode characters

       For example,




       Special Cases

       o   Bit Complement Operator ~ And vec()

	   The bit complement operator "~" may produce surprising results if used on strings con-
	   taining characters with ordinal values above 255. In such a case, the results are con-
	   sistent with the internal encoding of the characters, but not with much else. So don't
	   do that. Similarly for "vec()": you will be operating on the internally-encoded bit
	   patterns of the Unicode characters, not on the code point values, which is very proba-
	   bly not what you want.

       o   Peeking At Perl's Internal Encoding

	   Normal users of Perl should never care how Perl encodes any particular Unicode string
	   (because the normal ways to get at the contents of a string with Unicode--via input
	   and output--should always be via explicitly-defined I/O layers). But if you must,
	   there are two ways of looking behind the scenes.

	   One way of peeking inside the internal encoding of Unicode characters is to use
	   "unpack("C*", ..." to get the bytes or "unpack("H*", ...)"  to display the bytes:

	       # this prints  c4 80  for the UTF-8 bytes 0xc4 0x80
	       print join(" ", unpack("H*", pack("U", 0x100))), "\n";

	   Yet another way would be to use the Devel::Peek module:

	       perl -MDevel::Peek -e 'Dump(chr(0x100))'

	   That shows the UTF8 flag in FLAGS and both the UTF-8 bytes and Unicode characters in
	   "PV".  See also later in this document the discussion about the "is_utf8" function of
	   the "Encode" module.

       Advanced Topics

       o   String Equivalence

	   The question of string equivalence turns somewhat complicated in Unicode: what do you
	   mean by "equal"?


	   The short answer is that by default Perl compares equivalence ("eq", "ne") based only
	   on code points of the characters.  In the above case, the answer is no (because 0x00C1
	   != 0x0041).	But sometimes, any CAPITAL LETTER As should be considered equal, or even
	   As of any case.

	   The long answer is that you need to consider character normalization and casing
	   issues: see Unicode::Normalize, Unicode Technical Reports #15 and #21, Unicode Normal-
	   ization Forms and Case Mappings, http://www.unicode.org/unicode/reports/tr15/ and

	   As of Perl 5.8.0, the "Full" case-folding of Case Mappings/SpecialCasing is imple-

       o   String Collation

	   People like to see their strings nicely sorted--or as Unicode parlance goes, collated.
	   But again, what do you mean by collate?


	   The short answer is that by default, Perl compares strings ("lt", "le", "cmp", "ge",
	   "gt") based only on the code points of the characters.  In the above case, the answer
	   is "after", since 0x00C1 > 0x00C0.

	   The long answer is that "it depends", and a good answer cannot be given without know-
	   ing (at the very least) the language context.  See Unicode::Collate, and Unicode Col-
	   lation Algorithm http://www.unicode.org/unicode/reports/tr10/


       o   Character Ranges and Classes

	   Character ranges in regular expression character classes ("/[a-z]/") and in the
	   "tr///" (also known as "y///") operator are not magically Unicode-aware.  What this
	   means that "[A-Za-z]" will not magically start to mean "all alphabetic letters"; not
	   that it does mean that even for 8-bit characters, you should be using "/[[:alpha:]]/"
	   in that case.

	   For specifying character classes like that in regular expressions, you can use the
	   various Unicode properties--"\pL", or perhaps "\p{Alphabetic}", in this particular
	   case.  You can use Unicode code points as the end points of character ranges, but
	   there is no magic associated with specifying a certain range.  For further informa-
	   tion--there are dozens of Unicode character classes--see perlunicode.

       o   String-To-Number Conversions

	   Unicode does define several other decimal--and numeric--characters besides the famil-
	   iar 0 to 9, such as the Arabic and Indic digits.  Perl does not support string-to-num-
	   ber conversion for digits other than ASCII 0 to 9 (and ASCII a to f for hexadecimal).

       Questions With Answers

       o   Will My Old Scripts Break?

	   Very probably not.  Unless you are generating Unicode characters somehow, old behav-
	   iour should be preserved.  About the only behaviour that has changed and which could
	   start generating Unicode is the old behaviour of "chr()" where supplying an argument
	   more than 255 produced a character modulo 255.  "chr(300)", for example, was equal to
	   "chr(45)" or "-" (in ASCII), now it is LATIN CAPITAL LETTER I WITH BREVE.

       o   How Do I Make My Scripts Work With Unicode?

	   Very little work should be needed since nothing changes until you generate Unicode
	   data.  The most important thing is getting input as Unicode; for that, see the earlier
	   I/O discussion.

       o   How Do I Know Whether My String Is In Unicode?

	   You shouldn't care.	No, you really shouldn't.  No, really.	If you have to
	   care--beyond the cases described above--it means that we didn't get the transparency
	   of Unicode quite right.

	   Okay, if you insist:

	       use Encode 'is_utf8';
	       print is_utf8($string) ? 1 : 0, "\n";

	   But note that this doesn't mean that any of the characters in the string are necessary
	   UTF-8 encoded, or that any of the characters have code points greater than 0xFF(255)
	   or even 0x80(128), or that the string has any characters at all.  All the "is_utf8()"
	   does is to return the value of the internal "utf8ness" flag attached to the $string.
	   If the flag is off, the bytes in the scalar are interpreted as a single byte encoding.
	   If the flag is on, the bytes in the scalar are interpreted as the (multi-byte, vari-
	   able-length) UTF-8 encoded code points of the characters.  Bytes added to an UTF-8
	   encoded string are automatically upgraded to UTF-8.	If mixed non-UTF8 and UTF-8
	   scalars are merged (double-quoted interpolation, explicit concatenation, and
	   printf/sprintf parameter substitution), the result will be UTF-8 encoded as if copies
	   of the byte strings were upgraded to UTF-8: for example,

	       $a = "ab\x80c";
	       $b = "\x{100}";
	       print "$a = $b\n";

	   the output string will be UTF-8-encoded "ab\x80c\x{100}\n", but note that $a will stay

	   Sometimes you might really need to know the byte length of a string instead of the
	   character length. For that use either the "Encode::encode_utf8()" function or the
	   "bytes" pragma and its only defined function "length()":

	       my $unicode = chr(0x100);
	       print length($unicode), "\n"; # will print 1
	       require Encode;
	       print length(Encode::encode_utf8($unicode)), "\n"; # will print 2
	       use bytes;
	       print length($unicode), "\n"; # will also print 2
					     # (the 0xC4 0x80 of the UTF-8)

       o   How Do I Detect Data That's Not Valid In a Particular Encoding?

	   Use the "Encode" package to try converting it.  For example,

	       use Encode 'encode_utf8';
	       if (encode_utf8($string_of_bytes_that_I_think_is_utf8)) {
		   # valid
	       } else {
		   # invalid

	   For UTF-8 only, you can use:

	       use warnings;
	       @chars = unpack("U0U*", $string_of_bytes_that_I_think_is_utf8);

	   If invalid, a "Malformed UTF-8 character (byte 0x##) in unpack" warning is produced.
	   The "U0" means "expect strictly UTF-8 encoded Unicode".  Without that the
	   "unpack("U*", ...)" would accept also data like "chr(0xFF"), similarly to the "pack"
	   as we saw earlier.

       o   How Do I Convert Binary Data Into a Particular Encoding, Or Vice Versa?

	   This probably isn't as useful as you might think.  Normally, you shouldn't need to.

	   In one sense, what you are asking doesn't make much sense: encodings are for charac-
	   ters, and binary data are not "characters", so converting "data" into some encoding
	   isn't meaningful unless you know in what character set and encoding the binary data is
	   in, in which case it's not just binary data, now is it?

	   If you have a raw sequence of bytes that you know should be interpreted via a particu-
	   lar encoding, you can use "Encode":

	       use Encode 'from_to';
	       from_to($data, "iso-8859-1", "utf-8"); # from latin-1 to utf-8

	   The call to "from_to()" changes the bytes in $data, but nothing material about the
	   nature of the string has changed as far as Perl is concerned.  Both before and after
	   the call, the string $data contains just a bunch of 8-bit bytes. As far as Perl is
	   concerned, the encoding of the string remains as "system-native 8-bit bytes".

	   You might relate this to a fictional 'Translate' module:

	      use Translate;
	      my $phrase = "Yes";
	      Translate::from_to($phrase, 'english', 'deutsch');
	      ## phrase now contains "Ja"

	   The contents of the string changes, but not the nature of the string.  Perl doesn't
	   know any more after the call than before that the contents of the string indicates the

	   Back to converting data.  If you have (or want) data in your system's native 8-bit
	   encoding (e.g. Latin-1, EBCDIC, etc.), you can use pack/unpack to convert to/from Uni-

	       $native_string  = pack("C*", unpack("U*", $Unicode_string));
	       $Unicode_string = pack("U*", unpack("C*", $native_string));

	   If you have a sequence of bytes you know is valid UTF-8, but Perl doesn't know it yet,
	   you can make Perl a believer, too:

	       use Encode 'decode_utf8';
	       $Unicode = decode_utf8($bytes);

	   You can convert well-formed UTF-8 to a sequence of bytes, but if you just want to con-
	   vert random binary data into UTF-8, you can't.  Any random collection of bytes isn't
	   well-formed UTF-8.  You can use "unpack("C*", $string)" for the former, and you can
	   create well-formed Unicode data by "pack("U*", 0xff, ...)".

       o   How Do I Display Unicode?  How Do I Input Unicode?

	   See http://www.alanwood.net/unicode/ and http://www.cl.cam.ac.uk/~mgk25/unicode.html

       o   How Does Unicode Work With Traditional Locales?

	   In Perl, not very well.  Avoid using locales through the "locale" pragma.  Use only
	   one or the other.

       Hexadecimal Notation

       The Unicode standard prefers using hexadecimal notation because that more clearly shows
       the division of Unicode into blocks of 256 characters.  Hexadecimal is also simply shorter
       than decimal.  You can use decimal notation, too, but learning to use hexadecimal just
       makes life easier with the Unicode standard.  The "U+HHHH" notation uses hexadecimal, for

       The "0x" prefix means a hexadecimal number, the digits are 0-9 and a-f (or A-F, case
       doesn't matter).  Each hexadecimal digit represents four bits, or half a byte.  "print
       0x..., "\n"" will show a hexadecimal number in decimal, and "printf "%x\n", $decimal" will
       show a decimal number in hexadecimal.  If you have just the "hex digits" of a hexadecimal
       number, you can use the "hex()" function.

	   print 0x0009, "\n";	  # 9
	   print 0x000a, "\n";	  # 10
	   print 0x000f, "\n";	  # 15
	   print 0x0010, "\n";	  # 16
	   print 0x0011, "\n";	  # 17
	   print 0x0100, "\n";	  # 256

	   print 0x0041, "\n";	  # 65

	   printf "%x\n",  65;	  # 41
	   printf "%#x\n", 65;	  # 0x41

	   print hex("41"), "\n"; # 65

       Further Resources

       o   Unicode Consortium


       o   Unicode FAQ


       o   Unicode Glossary


       o   Unicode Useful Resources


       o   Unicode and Multilingual Support in HTML, Fonts, Web Browsers and Other Applications


       o   UTF-8 and Unicode FAQ for Unix/Linux


       o   Legacy Character Sets


       o   The Unicode support files live within the Perl installation in the directory


	   in Perl 5.8.0 or newer, and


	   in the Perl 5.6 series.  (The renaming to lib/unicore was done to avoid naming con-
	   flicts with lib/Unicode in case-insensitive filesystems.)  The main Unicode data file
	   is UnicodeData.txt (or Unicode.301 in Perl 5.6.1.)  You can find the $Config{install-
	   privlib} by

	       perl "-V:installprivlib"

	   You can explore various information from the Unicode data files using the "Uni-
	   code::UCD" module.

       If you cannot upgrade your Perl to 5.8.0 or later, you can still do some Unicode process-
       ing by using the modules "Unicode::String", "Unicode::Map8", and "Unicode::Map", available
       from CPAN.  If you have the GNU recode installed, you can also use the Perl front-end
       "Convert::Recode" for character conversions.

       The following are fast conversions from ISO 8859-1 (Latin-1) bytes to UTF-8 bytes and
       back, the code works even with older Perl 5 versions.

	   # ISO 8859-1 to UTF-8

	   # UTF-8 to ISO 8859-1

       perlunicode, Encode, encoding, open, utf8, bytes, perlretut, Unicode::Collate, Uni-
       code::Normalize, Unicode::UCD

       Thanks to the kind readers of the perl5-porters@perl.org, perl-unicode@perl.org,
       linux-utf8@nl.linux.org, and unicore@unicode.org mailing lists for their valuable feed-

       Copyright 2001-2002 Jarkko Hietaniemi <jhi@iki.fi>

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

perl v5.8.0				    2003-02-18				  PERLUNIINTRO(1)

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