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RedHat 9 (Linux i386) - man page for encoding (redhat section 3pm)

encoding(3pm)			 Perl Programmers Reference Guide		    encoding(3pm)

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

	 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;
	 use utf8;
	 # now you can use kanji identifiers -- in euc-jp!

       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

       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.  You can write code in EUC-JP as follows:

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

       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

       The encoding pragma also modifies the filehandle disciplines 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 sym-
       bol of perl.\n".

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

       use encoding [ENCNAME] ;
	   Sets the script encoding to ENCNAME. Filehandle disciplines of STDIN and STDOUT are
	   set to ":encoding(ENCNAME)".  Note that STDERR will not be changed.

	   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.

	   Note that non-STD file handles remain unaffected.  Use "use open" or "binmode" to
	   change disciplines of those.

       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.

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


       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.

       Because of this nature, the use of this pragma inside the module is strongly discouraged
       (because the influence of this pragma lasts not only for the module but the script that
       uses).  But if you have to, make sure you say "no encoding" at the end of the module so
       you contain the influence of the pragma within the module.


       Notice that only literals (string or regular expression) having only legacy code points
       are affected: if you mix data like this


       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

       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

       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.

       tr/// with ranges remain unaffected

       The encoding pragma works by decoding string literals in "q//,qq//,qr//,qw///, qx//" and
       so forth.  As of 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

       workaround to tr///;

       You can, however, achieve the same as simply as follows;

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

       Note the "tr//" expression is surronded 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.  In future version of perl, this
       counter-intuitive behaviour of "tr///" will be fixed so "eval qq{}" trick will be unnecce-

Non-ASCII Identifiers and 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.

       In other words, the same restriction as with Jperl applies.

       If you dare to experiment, however, you can try the Filter option.

       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.  In this case, STDIN and STDOUT remain untouched.

       What does this mean?  Your source code behaves as if it is written in UTF-8.  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.

       To make your script in legacy encoding work with minimum effort, do not use Filter=>1.

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;

       For native multibyte encodings (either fixed or variable length), the current implementa-
       tion of the regular expressions may introduce recoding errors for regular expression lit-
       erals longer than 127 bytes.

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

       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

perl v5.8.0				    2002-06-01				    encoding(3pm)

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