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NAME    [Toc]    [Back]

       perluniintro - Perl Unicode introduction

DESCRIPTION    [Toc]    [Back]

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

       Unicode    [Toc]    [Back]

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

       Unicode and ISO/IEC 10646 are coordinated standards that
       provide code points for characters 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.  Unicode 1.0 was released in October
       1991, and 4.0 in April 2003.

       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
       display-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 hexadecimal code
       point and the normative name of the character.

       Unicode also defines various properties for the characters,
 like "uppercase" or "lowercase", "decimal digit", or
       "punctuation"; these properties are independent of the
       names of the characters.  Furthermore, various operations
       on the characters like uppercasing, lowercasing, 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 sequence.

       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 "character", 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 character.

       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
       character".  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

       A common myth about Unicode is that it would be "16-bit",
       that is, Unicode is only represented as 0x10000 (or 65536)
       characters from 0x0000 to 0xFFFF.  This is untrue.  Since
       Unicode 2.0 (July 1996), Unicode has been defined all the
       way up to 21 bits (0x10FFFF), and since Unicode 3.1 (March
       2001), 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
       (yes, seventeen) planes in all were defined--but they are
       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 Unicode::UCD.

       The Unicode code points are just abstract numbers.  To
       input and output these abstract numbers, the numbers must
       be encoded or serialised 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 characters).  Other encodings
       include UTF-16 and UTF-32 and their big- and little-endian
       variants (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

       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
       maintenance 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 characters.  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. Specifically, 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 character beyond

       For example,

             perl -e 'print "F}0, "F}0'

       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 program's warning.

       You can enable automatic UTF-8-ification of your standard
       file handles, default "open()" layer, and @ARGV by using
       either the "-C" command line switch or the "PERL_UNICODE"
       environment variable, see perlrun for the documentation of
       the "-C" switch.

       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

       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 running "perl -V" and looking for "useperlio=define".

       Unicode and EBCDIC    [Toc]    [Back]

       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
  Unicode 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 "EBCDIC-safe".

       Creating Unicode    [Toc]    [Back]

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

           my $smiley = "}";

       Similarly, it can be used in regular expression literals

           $smiley =~ /}/;

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

           my $hebrew_alef = chr(0x05d0);

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

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

       Note that "." (no "{}" and only two hexadecimal digits),
 ".}", and "chr(...)" for arguments less than
       0x100 (decimal 256) generate an eight-bit character for
       backward compatibility 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 ".", ".}", or "chr()".

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

           use charnames ':full';
           my $arabic_alef = "RABIC LETTER ALEF}";

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

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

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

       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

          my $chars = pack("U0C*", 0x80, 0x42);

       Likewise, you can force the result to be bytes by using
       the special "C0" prefix.

       Handling Unicode    [Toc]    [Back]

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

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

           use charnames ':full';
           print length("ATIN CAPITAL LETTER A}OMBINING ACUTE ACCENT}"), "0;

       will print 2, not 1.  The only exception is that regular
       expressions have "

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

       Legacy Encodings    [Toc]    [Back]

       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
       assumption 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 'decode';
           $data  =  decode("iso-8859-3",  $data); # convert from
legacy to utf-8

       Unicode I/O

       Normally, writing out Unicode data

           print FH $some_string_with_unicode, "0;

       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 examples:

           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 ":encoding()" 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,
       specify 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

           use  open  ':utf8';  #  input and output default layer
will be UTF-8
           open X, ">file";
           print X chr(0x100), "0;
           close X;
           open Y, "<file";
           printf "%#x0, ord(<Y>); # this should print 0x100
           close Y;

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

           BEGIN { $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 "%#x0, ord(<I>), "0; # 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()" call.

       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)',
           open(my               $unicode,              '>:utf8',
           while (<$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 understood.

       Common encodings recognized by ISO, MIME, IANA, and various
 other standardisation organisations 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:

           # BAD CODE WARNING
           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 UTF-8.

       NOTE: the ":utf8" and ":encoding" features work only if
       your Perl has been built with the new PerlIO feature
       (which is the default on most systems).

       Displaying Unicode As Text    [Toc]    [Back]

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

       For example,


       returns the string


       which is ready to be printed.

       Special Cases    [Toc]    [Back]

       o   Bit Complement Operator ~ And vec()

           The bit complement operator "~" may produce surprising
           results if used on strings containing characters with
           ordinal values above 255. In such a case, the results
           are consistent 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
           probably 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

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

           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
           "utf8::is_utf8()" function.

       Advanced Topics    [Toc]    [Back]

       o   String Equivalence

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

           (Is "LATIN CAPITAL LETTER A WITH ACUTE" equal to

           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
           Normalization Forms and Case Mappings, http://www.uni-
           code.org/unicode/reports/tr15/ and http://www.uni-

           As of Perl 5.8.0, the "Full" case-folding of Case Map-
           pings/SpecialCasing is implemented.

       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?

           (Does "LATIN CAPITAL LETTER A WITH ACUTE" come before
           or after "LATIN CAPITAL LETTER A WITH GRAVE"?)

           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 knowing (at the very
           least) the language context.  See Unicode::Collate,
           and Unicode Collation Algorithm http://www.uni-

       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--"L",

or                     perhaps                    "{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
 information--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 familiar 0 to 9, such
           as the Arabic and Indic digits.  Perl does not support
           string-to-number conversion for digits other than
           ASCII 0 to 9 (and ASCII a to f for hexadecimal).

       Questions With Answers    [Toc]    [Back]

       o   Will My Old Scripts Break?

           Very probably not.  Unless you are generating Unicode
           characters somehow, old behaviour 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

       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:

               print utf8::is_utf8($string) ? 1 : 0, "0;

           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, variable-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-UTF-8 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

               $a = "ab0c";
               $b = "";

               print "$a = $b0;

           the output string will be UTF-8-encoded "ab0c =
           0, but $a will stay byte-encoded.

           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

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

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

           Use the "Encode" package to try converting it.  For
               use Encode 'decode_utf8';
               if                                            (decode_utf8($string_of_bytes_that_I_think_is_utf8)) {
                   # valid
               } else {
                   # invalid

           For UTF-8 only, you can use:

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

           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 characters, 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 particular 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

           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 affirmative.

           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 Unicode.

               $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 convert 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

       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.  But
           see perlrun for the description of the "-C" switch and
           its environment counterpart, $ENV{PERL_UNICODE} to see
           how to enable various Unicode features, for example by
           using locale settings.

       Hexadecimal Notation    [Toc]    [Back]

       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 example.

       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..., "0" will show a hexadecimal number in decimal,
 and "printf "%x0, $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, "0;    # 9
           print 0x000a, "0;    # 10
           print 0x000f, "0;    # 15
           print 0x0010, "0;    # 16
           print 0x0011, "0;    # 17
           print 0x0100, "0;    # 256

           print 0x0041, "0;    # 65

           printf "%x0,  65;    # 41
           printf "%#x0, 65;    # 0x41

           print hex("41"), "0; # 65

       Further Resources    [Toc]    [Back]

       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 conflicts 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{installprivlib} by

               perl "-V:installprivlib"

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


       If you cannot upgrade your Perl to 5.8.0 or later, you can
       still do some Unicode processing 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

SEE ALSO    [Toc]    [Back]

       perlunicode, Encode, encoding, open, utf8, bytes, perlretut,
 perlrun, Unicode::Collate, Unicode::Normalize, Unicode::UCD

ACKNOWLEDGMENTS    [Toc]    [Back]

       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 feedback.

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

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

perl v5.8.5                 2002-11-06                         17
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