  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 Unicodesupport. You could apply substr() and regexes even to complex CJKcharacters -- so long as the script was written in UTF-8. But backthen, text editors that supported UTF-8 were still rare and many usersinstead chose to write scripts in legacy encodings, giving up a wholenew feature of Perl 5.6.

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

Internally converts all literals (q//,qq//,qr//,qw///, qx//) fromthe encoding specified to utf8. In Perl 5.8.1 and later, literals intr/// and DATA pseudo-filehandle are also converted.
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 asthe 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 ofSTDIN 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 stringswith Unicode character data are concatenated, the new string willbe created by decoding the byte strings as ISO 8859-1 (Latin-1).

The encoding pragma changes this to use the specified encodinginstead. 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. Withoutuse encoding 'utf8';, it will print 4 instead, since $stringis three octets when interpreted as Latin-1.

Side effects

If the encoding pragma is in scope then the lengths returned arecalculated from the length of $/ in Unicode characters, which is notalways 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. Mostof these are done by Inaba Hiroto. Any other features and changesare good for 5.8.0.

"NON-EUC" doublebyte encodings
Because perl needs to parse script before applying this pragma, suchencodings as Shift_JIS and Big-5 that may contain '\' (BACKSLASH;\x5c) in the second byte fails because the second byte mayaccidentally escape the quoting character that follows. Perl 5.8.1or later fixes this problem.
tr//
tr// was overlooked by Perl 5 porters when they released perl 5.8.0See 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 useopen or binmode to change layers of those.
If no encoding is specified, the environment variable PERL_ENCODINGis 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 theSTDIN => ENCNAME form. In this case, you cannot omit thefirst ENCNAME. STDIN => undef turns the IO transcodingcompletely off.
When ${^UNICODE} exists and non-zero, these options will completelyignored. ${^UNICODE} is a variable introduced in perl 5.8.1. Seeperlrun see ${^UNICODE} in perlvar and -C in perlrun fordetails (perl 5.8.1 and later).
use encoding ENCNAME Filter=>1;
This turns the encoding pragma into a source filter. While thedefault approach just decodes interpolated literals (in qq() andqr()), this will apply a source filter to the entire source code. SeeThe Filter Option below for details.
no encoding;
Unsets the script encoding. The layers of STDIN, STDOUT arereset to ":raw" (the default unprocessed raw stream of bytes).

The Filter Option

The magic of use encoding is not applied to the names ofidentifiers. In order to make ${"\x{4eba}"}++ ($human++, where humanis a single Han ideograph) work, you still need to write your scriptin 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 inUTF-8 with 'use utf8' in effect. So even if your editor only supportsShift_JIS, for example, you can still try examples in Chapter 15 ofProgramming Perl, 3rd Ed.. For instance, you can use UTF-8identifiers.

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

Filter-related changes at Encode version 1.87

The Filter option now sets STDIN and STDOUT like non-filter options.And STDIN=>ENCODING and STDOUT=>ENCODING work likenon-filter version.
use utf8 is implicitly declared so you no longer have to useutf8 to ${"\x{4eba}"}++.

CAVEATS

NOT SCOPED

The pragma is a per script, not a per block lexical. Only the lastuse encoding or no encoding matters, and it affectsthe whole script. However, the <no encoding> pragma is supported anduse 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 alsodiscouraged (though not as strongly discouraged as the case above.See below).

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

  # 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 AFTERother 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 onlylegacy 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 nativeencoding. 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) onthe left will not be upgraded to \x{3af} (Unicode GREEK SMALLLETTER IOTA WITH TONOS) because of the \x{100} on the left. Youshould 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 (unlessthey are combined with characters with code points 0x100 or larger,in which case all characters need to become UTF-8 encoded), but ifthe encoding pragma is present, even the 0x80..0xFF range alwaysgets UTF-8 encoded.

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

tr/// with ranges

The encoding pragma works by decoding string literals inq//,qq//,qr//,qw///, qx// and so forth. In perl 5.8.0, thisdoes 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 behindis 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 sotr/// not being decoded was obviously against the will of Perl5Porters 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
 
  $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 introducerecoding 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 arewelcome.)
format
This pragma doesn't work well with format because PerlIO does notget along very well with it. When format contains non-asciicharacters 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
 
```
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 tounicode characters since you have to consider such things as characterwidth (i.e. double-width for ideographs) and directions (i.e. BIDI forArabic and Hebrew).
Thread safety
use encoding ... is not thread-safe (i.e., do not use in threadedapplications).

The Logic of :locale

The logic of :locale is as follows:

1.: If the platform supports the langinfo(CODESET) interface, the codesetreturned is used as the default encoding for the open pragma.
2.: If 1. didn't work but we are under the locale pragma, the environmentvariables LC_ALL and LANG (in that order) are matched for encodings(the part after ., if any), and if any found, that is usedas 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 ifany found, :utf8 is used as the default encoding for the openpragma.

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 ofany subsequent file open, is UTF-8.

HISTORY

This pragma first appeared in Perl 5.8.0. For features that require5.8.1 and better, see above.

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

Allows you to write your script in non-ascii or non-utf8

Daftar Isi

NAME

SYNOPSIS