


ext::Encode::encoPerl(Programmers Refereext::Encode::encoding(3p)


NAME
       encoding - allows you to write your script in non-ascii or
       non-utf8

SYNOPSIS
         use encoding "greek";  # Perl like Greek to you?
         use encoding "euc-jp"; # Jperl!

         # or you can even do this if your shell supports your native encoding

         perl -Mencoding=latin2 -e'...' # Feeling centrally European?
         perl -Mencoding=euc-kr -e'...' # Or Korean?

         # more control

         # A simple euc-cn => utf-8 converter
         use encoding "euc-cn", STDOUT => "utf8";  while(<>){print};

         # "no encoding;" supported (but not scoped!)
         no encoding;

         # an alternate way, Filter
         use encoding "euc-jp", Filter=>1;
         # now you can use kanji identifiers -- in euc-jp!

         # switch on locale -
         # note that this probably means that unless you have a complete control
         # over the environments the application is ever going to be run, you should
         # NOT use the feature of encoding pragma allowing you to write your script
         # in any recognized encoding because changing locale settings will wreck
         # the script; you can of course still use the other features of the pragma.
         use encoding ':locale';

ABSTRACT
       Let's start with a bit of history: Perl 5.6.0 introduced
       Unicode support.  You could apply "substr()" and regexes
       even to complex CJK characters -- so long as the script
       was written in UTF-8.  But back then, text editors that
       supported UTF-8 were still rare and many users instead
       chose to write scripts in legacy encodings, giving up a
       whole new feature of Perl 5.6.

       Rewind to the future: starting from perl 5.8.0 with the
       encoding pragma, you can write your script in any encoding
       you like (so long as the "Encode" module supports it) and
       still enjoy Unicode support.  This pragma achieves that by
       doing the following:

       o   Internally converts all literals
           ("q//,qq//,qr//,qw///, qx//") from the encoding
           specified to utf8.  In Perl 5.8.1 and later, literals
           in "tr///" and "DATA" pseudo-filehandle are also
           converted.




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ext::Encode::encoPerl(Programmers Refereext::Encode::encoding(3p)


       o   Changing PerlIO layers of "STDIN" and "STDOUT" to the
           encoding
            specified.

   Literal Conversions
       You can write code in EUC-JP as follows:

         my $Rakuda = "\xF1\xD1\xF1\xCC"; # Camel in Kanji
                      #<-char-><-char->   # 4 octets
         s/\bCamel\b/$Rakuda/;

       And with "use encoding "euc-jp"" in effect, it is the same
       thing as the code in UTF-8:

         my $Rakuda = "\x{99F1}\x{99DD}"; # two Unicode Characters
         s/\bCamel\b/$Rakuda/;

   PerlIO layers for "STD(IN|OUT)"
       The encoding pragma also modifies the filehandle layers of
       STDIN and STDOUT to the specified encoding.  Therefore,

         use encoding "euc-jp";
         my $message = "Camel is the symbol of perl.\n";
         my $Rakuda = "\xF1\xD1\xF1\xCC"; # Camel in Kanji
         $message =~ s/\bCamel\b/$Rakuda/;
         print $message;

       Will print "\xF1\xD1\xF1\xCC is the symbol of perl.\n",
       not "\x{99F1}\x{99DD} is the symbol of perl.\n".

       You can override this by giving extra arguments; see
       below.

   Implicit upgrading for byte strings
       By default, if strings operating under byte semantics and
       strings with Unicode character data are concatenated, the
       new string will be created by decoding the byte strings as
       ISO 8859-1 (Latin-1).

       The encoding pragma changes this to use the specified
       encoding instead.  For example:

           use encoding 'utf8';
           my $string = chr(20000); # a Unicode string
           utf8::encode($string);   # now it's a UTF-8 encoded byte string
           # concatenate with another Unicode string
           print length($string . chr(20000));

       Will print 2, because $string is upgraded as UTF-8.
       Without "use encoding 'utf8';", it will print 4 instead,
       since $string is three octets when interpreted as Latin-1.

   Side effects
       If the "encoding" pragma is in scope then the lengths



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ext::Encode::encoPerl(Programmers Refereext::Encode::encoding(3p)


       returned are calculated from the length of $/ in Unicode
       characters, which is not always the same as the length of
       $/ in the native encoding.

       This pragma affects utf8::upgrade, but not
       utf8::downgrade.

FEATURES THAT REQUIRE 5.8.1
       Some of the features offered by this pragma requires perl
       5.8.1.  Most of these are done by Inaba Hiroto.  Any other
       features and changes are good for 5.8.0.

       "NON-EUC" doublebyte encodings
           Because perl needs to parse script before applying
           this pragma, such encodings as Shift_JIS and Big-5
           that may contain '\' (BACKSLASH; \x5c) in the second
           byte fails because the second byte may accidentally
           escape the quoting character that follows.  Perl 5.8.1
           or later fixes this problem.

       tr//
           "tr//" was overlooked by Perl 5 porters when they
           released perl 5.8.0 See the section below for details.

       DATA pseudo-filehandle
           Another feature that was overlooked was "DATA".

USAGE
       use encoding [ENCNAME] ;
           Sets the script encoding to ENCNAME.  And unless
           ${^UNICODE} exists and non-zero, PerlIO layers of
           STDIN and STDOUT are set to ":encoding(ENCNAME)".

           Note that STDERR WILL NOT be changed.

           Also note that non-STD file handles remain unaffected.
           Use "use open" or "binmode" to change layers of those.

           If no encoding is specified, the environment variable
           PERL_ENCODING is consulted.  If no encoding can be
           found, the error "Unknown encoding 'ENCNAME'" will be
           thrown.

       use encoding ENCNAME [ STDIN => ENCNAME_IN ...] ;
           You can also individually set encodings of STDIN and
           STDOUT via the "STDIN => ENCNAME" form.  In this case,
           you cannot omit the first ENCNAME.  "STDIN => undef"
           turns the IO transcoding completely off.

           When ${^UNICODE} exists and non-zero, these options
           will completely ignored.  ${^UNICODE} is a variable
           introduced in perl 5.8.1.  See perlrun see
           "${^UNICODE}" in perlvar and "-C" in perlrun for
           details (perl 5.8.1 and later).



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ext::Encode::encoPerl(Programmers Refereext::Encode::encoding(3p)


       use encoding ENCNAME Filter=>1;
           This turns the encoding pragma into a source filter.
           While the default approach just decodes interpolated
           literals (in qq() and qr()), this will apply a source
           filter to the entire source code.  See "The Filter
           Option" below for details.

       no encoding;
           Unsets the script encoding. The layers of STDIN,
           STDOUT are reset to ":raw" (the default unprocessed
           raw stream of bytes).

The Filter Option
       The magic of "use encoding" is not applied to the names of
       identifiers.  In order to make "${"\x{4eba}"}++"
       ($human++, where human is a single Han ideograph) work,
       you still need to write your script in UTF-8 -- or use a
       source filter.  That's what 'Filter=>1' does.

       What does this mean?  Your source code behaves as if it is
       written in UTF-8 with 'use utf8' in effect.  So even if
       your editor only supports Shift_JIS, for example, you can
       still try examples in Chapter 15 of "Programming Perl, 3rd
       Ed.".  For instance, you can use UTF-8 identifiers.

       This option is significantly slower and (as of this
       writing) non-ASCII identifiers are not very stable WITHOUT
       this option and with the source code written in UTF-8.

   Filter-related changes at Encode version 1.87
       o   The Filter option now sets STDIN and STDOUT like non-
           filter options.  And "STDIN=>ENCODING" and
           "STDOUT=>ENCODING" work like non-filter version.

       o   "use utf8" is implicitly declared so you no longer
           have to "use utf8" to "${"\x{4eba}"}++".

CAVEATS
   NOT SCOPED
       The pragma is a per script, not a per block lexical.  Only
       the last "use encoding" or "no encoding" matters, and it
       affects the whole script.  However, the <no encoding>
       pragma is supported and use encoding can appear as many
       times as you want in a given script.  The multiple use of
       this pragma is discouraged.

       By the same reason, the use this pragma inside modules is
       also discouraged (though not as strongly discouraged as
       the case above.  See below).

       If you still have to write a module with this pragma, be
       very careful of the load order.  See the codes below;





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ext::Encode::encoPerl(Programmers Refereext::Encode::encoding(3p)


         # called module
         package Module_IN_BAR;
         use encoding "bar";
         # stuff in "bar" encoding here
         1;

         # caller script
         use encoding "foo"
         use Module_IN_BAR;
         # surprise! use encoding "bar" is in effect.

       The best way to avoid this oddity is to use this pragma
       RIGHT AFTER other modules are loaded.  i.e.

         use Module_IN_BAR;
         use encoding "foo";

   DO NOT MIX MULTIPLE ENCODINGS
       Notice that only literals (string or regular expression)
       having only legacy code points are affected: if you mix
       data like this

           \xDF\x{100}

       the data is assumed to be in (Latin 1 and) Unicode, not in
       your native encoding.  In other words, this will match in
       "greek":

           "\xDF" =~ /\x{3af}/

       but this will not

           "\xDF\x{100}" =~ /\x{3af}\x{100}/

       since the "\xDF" (ISO 8859-7 GREEK SMALL LETTER IOTA WITH
       TONOS) on the left will not be upgraded to "\x{3af}"
       (Unicode GREEK SMALL LETTER IOTA WITH TONOS) because of
       the "\x{100}" on the left.  You should not be mixing your
       legacy data and Unicode in the same string.

       This pragma also affects encoding of the 0x80..0xFF code
       point range: normally characters in that range are left as
       eight-bit bytes (unless they are combined with characters
       with code points 0x100 or larger, in which case all
       characters need to become UTF-8 encoded), but if the
       "encoding" pragma is present, even the 0x80..0xFF range
       always gets UTF-8 encoded.

       After all, the best thing about this pragma is that you
       don't have to resort to \x{....} just to spell your name
       in a native encoding.  So feel free to put your strings in
       your encoding in quotes and regexes.





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ext::Encode::encoPerl(Programmers Refereext::Encode::encoding(3p)


   tr/// with ranges
       The encoding pragma works by decoding string literals in
       "q//,qq//,qr//,qw///, qx//" and so forth.  In perl 5.8.0,
       this does not apply to "tr///".  Therefore,

         use encoding 'euc-jp';
         #....
         $kana =~ tr/\xA4\xA1-\xA4\xF3/\xA5\xA1-\xA5\xF3/;
         #           -------- -------- -------- --------

       Does not work as

         $kana =~ tr/\x{3041}-\x{3093}/\x{30a1}-\x{30f3}/;

       Legend of characters above
             utf8     euc-jp   charnames::viacode()
             -----------------------------------------
             \x{3041} \xA4\xA1 HIRAGANA LETTER SMALL A
             \x{3093} \xA4\xF3 HIRAGANA LETTER N
             \x{30a1} \xA5\xA1 KATAKANA LETTER SMALL A
             \x{30f3} \xA5\xF3 KATAKANA LETTER N

       This counterintuitive behavior has been fixed in perl
       5.8.1.

       workaround to tr///;

       In perl 5.8.0, you can work around as follows;

         use encoding 'euc-jp';
         #  ....
         eval qq{ \$kana =~ tr/\xA4\xA1-\xA4\xF3/\xA5\xA1-\xA5\xF3/ };

       Note the "tr//" expression is surrounded by "qq{}".  The
       idea behind is the same as classic idiom that makes
       "tr///" 'interpolate'.

          tr/$from/$to/;            # wrong!
          eval qq{ tr/$from/$to/ }; # workaround.

       Nevertheless, in case of encoding pragma even "q//" is
       affected so "tr///" not being decoded was obviously
       against the will of Perl5 Porters so it has been fixed in
       Perl 5.8.1 or later.

EXAMPLE - Greekperl
           use encoding "iso 8859-7";

           # \xDF in ISO 8859-7 (Greek) is \x{3af} in Unicode.

           $a = "\xDF";
           $b = "\x{100}";

           printf "%#x\n", ord($a); # will print 0x3af, not 0xdf



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ext::Encode::encoPerl(Programmers Refereext::Encode::encoding(3p)



           $c = $a . $b;

           # $c will be "\x{3af}\x{100}", not "\x{df}\x{100}".

           # chr() is affected, and ...

           print "mega\n"  if ord(chr(0xdf)) == 0x3af;

           # ... ord() is affected by the encoding pragma ...

           print "tera\n" if ord(pack("C", 0xdf)) == 0x3af;

           # ... as are eq and cmp ...

           print "peta\n" if "\x{3af}" eq  pack("C", 0xdf);
           print "exa\n"  if "\x{3af}" cmp pack("C", 0xdf) == 0;

           # ... but pack/unpack C are not affected, in case you still
           # want to go back to your native encoding

           print "zetta\n" if unpack("C", (pack("C", 0xdf))) == 0xdf;

KNOWN PROBLEMS
       literals in regex that are longer than 127 bytes
           For native multibyte encodings (either fixed or
           variable length), the current implementation of the
           regular expressions may introduce recoding errors for
           regular expression literals longer than 127 bytes.

       EBCDIC
           The encoding pragma is not supported on EBCDIC
           platforms.  (Porters who are willing and able to
           remove this limitation are welcome.)

       format
           This pragma doesn't work well with format because
           PerlIO does not get along very well with it.  When
           format contains non-ascii characters it prints funny
           or gets "wide character warnings".  To understand it,
           try the code below.

             # Save this one in utf8
             # replace *non-ascii* with a non-ascii string
             my $camel;
             format STDOUT =
             *non-ascii*@>>>>>>>
             $camel
             .
             $camel = "*non-ascii*";
             binmode(STDOUT=>':encoding(utf8)'); # bang!
             write;              # funny
             print $camel, "\n"; # fine




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ext::Encode::encoPerl(Programmers Refereext::Encode::encoding(3p)


           Without binmode this happens to work but without
           binmode, print() fails instead of write().

           At any rate, the very use of format is questionable
           when it comes to unicode characters since you have to
           consider such things as character width (i.e. double-
           width for ideographs) and directions (i.e. BIDI for
           Arabic and Hebrew).

       Thread safety
           "use encoding ..." is not thread-safe (i.e., do not
           use in threaded applications).

   The Logic of :locale
       The logic of ":locale" is as follows:

       1.  If the platform supports the langinfo(CODESET)
           interface, the codeset returned is used as the default
           encoding for the open pragma.

       2.  If 1. didn't work but we are under the locale pragma,
           the environment variables LC_ALL and LANG (in that
           order) are matched for encodings (the part after ".",
           if any), and if any found, that is used as the default
           encoding for the open pragma.

       3.  If 1. and 2. didn't work, the environment variables
           LC_ALL and LANG (in that order) are matched for
           anything looking like UTF-8, and if any found, ":utf8"
           is used as the default encoding for the open pragma.

       If your locale environment variables (LC_ALL, LC_CTYPE,
       LANG) contain the strings 'UTF-8' or 'UTF8' (case-
       insensitive matching), the default encoding of your STDIN,
       STDOUT, and STDERR, and of any subsequent file open, is
       UTF-8.

HISTORY
       This pragma first appeared in Perl 5.8.0.  For features
       that require 5.8.1 and better, see above.

       The ":locale" subpragma was implemented in 2.01, or Perl
       5.8.6.

SEE ALSO
       perlunicode, Encode, open, Filter::Util::Call,

       Ch. 15 of "Programming Perl (3rd Edition)" by Larry Wall,
       Tom Christiansen, Jon Orwant; O'Reilly & Associates; ISBN
       0-596-00027-8







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