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 encodingperl -Mencoding=latin2 -e '...' # Feeling centrally European?perl -Mencoding=euc-kr -e '...' # Or Korean?# more control# A simple euc-cn => utf-8 converteruse encoding "euc-cn", STDOUT => "utf8"; while(<>){print};# "no encoding;" supported (but not scoped!)no encoding;# an alternate way, Filteruse encoding "euc-jp", Filter=>1;# 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 applysubstr() 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 theencoding pragma, you can write your script in any encoding you like (so long as theEncode 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//) from the encoding specified to utf8. In Perl 5.8.1 and later, literals intr/// andDATA pseudo-filehandle are also converted.
Changing PerlIO layers ofSTDIN andSTDOUT to the encoding specified.
You can write code in EUC-JP as follows:
my $Rakuda = "\xF1\xD1\xF1\xCC"; # Camel in Kanji #<-char-><-char-> # 4 octetss/\bCamel\b/$Rakuda/;And withuse encoding "euc-jp" in effect, it is the same thing as the code in UTF-8:
my $Rakuda = "\x{99F1}\x{99DD}"; # two Unicode Characterss/\bCamel\b/$Rakuda/;STD(IN|OUT)Theencoding 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.
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.
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// was overlooked by Perl 5 porters when they released perl 5.8.0 See the section below for details.
Another feature that was overlooked wasDATA.
Sets the script encoding toENCNAME. 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. Useuse open orbinmode to change layers of those.
If no encoding is specified, the environment variablePERL_ENCODING is consulted. If no encoding can be found, the errorUnknown encoding 'ENCNAME' will be thrown.
You can also individually set encodings of STDIN and STDOUT via theSTDIN =>ENCNAME form. In this case, you cannot omit the firstENCNAME.STDIN => undef turns the IO transcoding completely off.
When ${^UNICODE} exists and non-zero, these options will completely ignored. ${^UNICODE} is a variable introduced in perl 5.8.1. Seeperlrun see"${^UNICODE}" in perlvar and"-C" in perlrun for details (perl 5.8.1 and later).
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.
Unsets the script encoding. The layers of STDIN, STDOUT are reset to ":raw" (the default unprocessed raw stream of bytes).
The magic ofuse 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 ofProgramming 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.
The Filter option now sets STDIN and STDOUT like non-filter options. AndSTDIN=>ENCODING andSTDOUT=>ENCODING work like non-filter version.
use utf8 is implicitly declared so you no longer have touse utf8 to${"\x{4eba}"}++.
The pragma is a per script, not a per block lexical. Only the lastuse encoding orno 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 also discouraged (though not as strongly discouranged 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;
# called modulepackage Module_IN_BAR;use encoding "bar";# stuff in "bar" encoding here1;# caller scriptuse 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";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 willnot 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 theencoding 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.
Theencoding pragma works by decoding string literals inq//,qq//,qr//,qw///, qx// and so forth. In perl 5.8.0, this does not apply totr///. Therefore,
use encoding 'euc-jp';#....$kana =~ tr/\xA4\xA1-\xA4\xF3/\xA5\xA1-\xA5\xF3/;# -------- -------- -------- --------Does not work as
$kana =~ tr/\x{3041}-\x{3093}/\x{30a1}-\x{30f3}/;utf8 euc-jp charnames::viacode()-----------------------------------------\x{3041} \xA4\xA1 HIRAGANA LETTER SMALL A\x{3093} \xA4\xF3 HIRAGANA LETTER N\x{30a1} \xA5\xA1 KATAKANA LETTER SMALL A\x{30f3} \xA5\xF3 KATAKANA LETTER NThis counterintuitive behavior has been fixed in perl 5.8.1.
In perl 5.8.0, you can work around as follows;
use encoding 'euc-jp';# ....eval qq{ \$kana =~ tr/\xA4\xA1-\xA4\xF3/\xA5\xA1-\xA5\xF3/ };Note thetr// expression is surrounded byqq{}. The idea behind is the same as classic idiom that makestr/// 'interpolate'.
tr/$from/$to/; # wrong!eval qq{ tr/$from/$to/ }; # workaround.Nevertheless, in case ofencoding pragma evenq// is affected sotr/// not being decoded was obviously against the will of Perl5 Porters so it has been fixed in Perl 5.8.1 or later.
use encoding "iso 8859-7";# \xDF in ISO 8859-7 (Greek) is \x{3af} in Unicode.$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 encodingprint "zetta\n" if unpack("C", (pack("C", 0xdf))) == 0xdf;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.
The encoding pragma is not supported on EBCDIC platforms. (Porters who are willing and able to remove this limitation are welcome.)
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 stringmy $camel;format STDOUT =*non-ascii*@>>>>>>>$camel.$camel = "*non-ascii*";binmode(STDOUT=>':encoding(utf8)'); # bang!write; # funny print $camel, "\n"; # fineWithout 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).
This pragma first appeared in Perl 5.8.0. For features that require 5.8.1 and better, see above.
perlunicode,Encode,open,Filter::Util::Call,
Ch. 15 ofProgramming Perl (3rd Edition) by Larry Wall, Tom Christiansen, Jon Orwant; O'Reilly & Associates; ISBN 0-596-00027-8
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