℞0:Standardpreamble
Unless otherwise notes, all examples below require this standard preamble to work correctly, with the
"#!" adjusted to work on your system:
#!/usr/bin/env perl
use v5.36; # or later to get "unicode_strings" feature,
# plus strict, warnings
use utf8; # so literals and identifiers can be in UTF-8
use warnings qw(FATAL utf8); # fatalize encoding glitches
use open qw(:std :encoding(UTF-8)); # undeclared streams in UTF-8
use charnames qw(:full :short); # unneeded in v5.16
This does make even Unix programmers "binmode" your binary streams, or open them with ":raw", but that's
the only way to get at them portably anyway.
WARNING: "use autodie" (pre 2.26) and "use open" do not get along with each other.
℞1:GenericUnicode-savvyfilter
Always decompose on the way in, then recompose on the way out.
use Unicode::Normalize;
while (<>) {
$_ = NFD($_); # decompose + reorder canonically
...
} continue {
print NFC($_); # recompose (where possible) + reorder canonically
}
℞2:Fine-tuningUnicodewarnings
As of v5.14, Perl distinguishes three subclasses of UTF‑8 warnings.
use v5.14; # subwarnings unavailable any earlier
no warnings "nonchar"; # the 66 forbidden non-characters
no warnings "surrogate"; # UTF-16/CESU-8 nonsense
no warnings "non_unicode"; # for codepoints over 0x10_FFFF
℞3:Declaresourceinutf8foridentifiersandliterals
Without the all-critical "use utf8" declaration, putting UTF‑8 in your literals and identifiers won’t
work right. If you used the standard preamble just given above, this already happened. If you did, you
can do things like this:
use utf8;
my $measure = "Ångström";
my @μsoft = qw( cp852 cp1251 cp1252 );
my @ὑπέρμεγας = qw( ὑπέρ μεγας );
my @鯉 = qw( koi8-f koi8-u koi8-r );
my $motto = "👪 💗 🐪"; # FAMILY, GROWING HEART, DROMEDARY CAMEL
If you forget "use utf8", high bytes will be misunderstood as separate characters, and nothing will work
right.
℞4:Charactersandtheirnumbers
The "ord" and "chr" functions work transparently on all codepoints, not just on ASCII alone — nor in
fact, not even just on Unicode alone.
# ASCII characters
ord("A")
chr(65)
# characters from the Basic Multilingual Plane
ord("Σ")
chr(0x3A3)
# beyond the BMP
ord("𝑛") # MATHEMATICAL ITALIC SMALL N
chr(0x1D45B)
# beyond Unicode! (up to MAXINT)
ord("\x{20_0000}")
chr(0x20_0000)
℞5:Unicodeliteralsbycharacternumber
In an interpolated literal, whether a double-quoted string or a regex, you may specify a character by its
number using the "\x{HHHHHH}" escape.
String: "\x{3a3}"
Regex: /\x{3a3}/
String: "\x{1d45b}"
Regex: /\x{1d45b}/
# even non-BMP ranges in regex work fine
/[\x{1D434}-\x{1D467}]/
℞6:Getcharacternamebynumber
use charnames ();
my $name = charnames::viacode(0x03A3);
℞7:Getcharacternumberbyname
use charnames ();
my $number = charnames::vianame("GREEK CAPITAL LETTER SIGMA");
℞8:Unicodenamedcharacters
Use the "\N{charname}" notation to get the character by that name for use in interpolated literals
(double-quoted strings and regexes). In v5.16, there is an implicit
use charnames qw(:full :short);
But prior to v5.16, you must be explicit about which set of charnames you want. The ":full" names are
the official Unicode character name, alias, or sequence, which all share a namespace.
use charnames qw(:full :short latin greek);
"\N{MATHEMATICAL ITALIC SMALL N}" # :full
"\N{GREEK CAPITAL LETTER SIGMA}" # :full
Anything else is a Perl-specific convenience abbreviation. Specify one or more scripts by names if you
want short names that are script-specific.
"\N{Greek:Sigma}" # :short
"\N{ae}" # latin
"\N{epsilon}" # greek
The v5.16 release also supports a ":loose" import for loose matching of character names, which works just
like loose matching of property names: that is, it disregards case, whitespace, and underscores:
"\N{euro sign}" # :loose (from v5.16)
Starting in v5.32, you can also use
qr/\p{name=euro sign}/
to get official Unicode named characters in regular expressions. Loose matching is always done for
these.
℞9:Unicodenamedsequences
These look just like character names but return multiple codepoints. Notice the %vx vector-print
functionality in "printf".
use charnames qw(:full);
my $seq = "\N{LATIN CAPITAL LETTER A WITH MACRON AND GRAVE}";
printf "U+%v04X\n", $seq;
U+0100.0300
℞10:Customnamedcharacters
Use ":alias" to give your own lexically scoped nicknames to existing characters, or even to give unnamed
private-use characters useful names.
use charnames ":full", ":alias" => {
ecute => "LATIN SMALL LETTER E WITH ACUTE",
"APPLE LOGO" => 0xF8FF, # private use character
};
"\N{ecute}"
"\N{APPLE LOGO}"
℞11:NamesofCJKcodepoints
Sinograms like “東京” come back with character names of "CJK UNIFIED IDEOGRAPH-6771" and "CJK UNIFIED
IDEOGRAPH-4EAC", because their “names” vary. The CPAN "Unicode::Unihan" module has a large database for
decoding these (and a whole lot more), provided you know how to understand its output.
# cpan -i Unicode::Unihan
use Unicode::Unihan;
my $str = "東京";
my $unhan = Unicode::Unihan->new;
for my $lang (qw(Mandarin Cantonese Korean JapaneseOn JapaneseKun)) {
printf "CJK $str in %-12s is ", $lang;
say $unhan->$lang($str);
}
prints:
CJK 東京 in Mandarin is DONG1JING1
CJK 東京 in Cantonese is dung1ging1
CJK 東京 in Korean is TONGKYENG
CJK 東京 in JapaneseOn is TOUKYOU KEI KIN
CJK 東京 in JapaneseKun is HIGASHI AZUMAMIYAKO
If you have a specific romanization scheme in mind, use the specific module:
# cpan -i Lingua::JA::Romanize::Japanese
use Lingua::JA::Romanize::Japanese;
my $k2r = Lingua::JA::Romanize::Japanese->new;
my $str = "東京";
say "Japanese for $str is ", $k2r->chars($str);
prints
Japanese for 東京 is toukyou
℞12:Explicitencode/decode
On rare occasion, such as a database read, you may be given encoded text you need to decode.
use Encode qw(encode decode);
my $chars = decode("shiftjis", $bytes, 1);
# OR
my $bytes = encode("MIME-Header-ISO_2022_JP", $chars, 1);
For streams all in the same encoding, don't use encode/decode; instead set the file encoding when you
open the file or immediately after with "binmode" as described later below.
℞13:Decodeprogramargumentsasutf8
$ perl -CA ...
or
$ export PERL_UNICODE=A
or
use Encode qw(decode);
@ARGV = map { decode('UTF-8', $_, 1) } @ARGV;
℞14:Decodeprogramargumentsaslocaleencoding
# cpan -i Encode::Locale
use Encode qw(locale);
use Encode::Locale;
# use "locale" as an arg to encode/decode
@ARGV = map { decode(locale => $_, 1) } @ARGV;
℞15:DeclareSTD{IN,OUT,ERR}tobeutf8
Use a command-line option, an environment variable, or else call "binmode" explicitly:
$ perl -CS ...
or
$ export PERL_UNICODE=S
or
use open qw(:std :encoding(UTF-8));
or
binmode(STDIN, ":encoding(UTF-8)");
binmode(STDOUT, ":utf8");
binmode(STDERR, ":utf8");
℞16:DeclareSTD{IN,OUT,ERR}tobeinlocaleencoding
# cpan -i Encode::Locale
use Encode;
use Encode::Locale;
# or as a stream for binmode or open
binmode STDIN, ":encoding(console_in)" if -t STDIN;
binmode STDOUT, ":encoding(console_out)" if -t STDOUT;
binmode STDERR, ":encoding(console_out)" if -t STDERR;
℞17:MakefileI/Odefaulttoutf8
Files opened without an encoding argument will be in UTF-8:
$ perl -CD ...
or
$ export PERL_UNICODE=D
or
use open qw(:encoding(UTF-8));
℞18:MakeallI/Oandargsdefaulttoutf8
$ perl -CSDA ...
or
$ export PERL_UNICODE=SDA
or
use open qw(:std :encoding(UTF-8));
use Encode qw(decode);
@ARGV = map { decode('UTF-8', $_, 1) } @ARGV;
℞19:Openfilewithspecificencoding
Specify stream encoding. This is the normal way to deal with encoded text, not by calling low-level
functions.
# input file
open(my $in_file, "< :encoding(UTF-16)", "wintext");
OR
open(my $in_file, "<", "wintext");
binmode($in_file, ":encoding(UTF-16)");
THEN
my $line = <$in_file>;
# output file
open($out_file, "> :encoding(cp1252)", "wintext");
OR
open(my $out_file, ">", "wintext");
binmode($out_file, ":encoding(cp1252)");
THEN
print $out_file "some text\n";
More layers than just the encoding can be specified here. For example, the incantation ":raw
:encoding(UTF-16LE) :crlf" includes implicit CRLF handling.
℞20:Unicodecasing
Unicode casing is very different from ASCII casing.
uc("henry ⅷ") # "HENRY Ⅷ"
uc("tschüß") # "TSCHÜSS" notice ß => SS
# both are true:
"tschüß" =~ /TSCHÜSS/i # notice ß => SS
"Σίσυφος" =~ /ΣΊΣΥΦΟΣ/i # notice Σ,σ,ς sameness
℞21:Unicodecase-insensitivecomparisons
Also available in the CPAN Unicode::CaseFold module, the new "fc" “foldcase” function from v5.16 grants
access to the same Unicode casefolding as the "/i" pattern modifier has always used:
use feature "fc"; # fc() function is from v5.16
# sort case-insensitively
my @sorted = sort { fc($a) cmp fc($b) } @list;
# both are true:
fc("tschüß") eq fc("TSCHÜSS")
fc("Σίσυφος") eq fc("ΣΊΣΥΦΟΣ")
℞22:MatchUnicodelinebreaksequenceinregex
A Unicode linebreak matches the two-character CRLF grapheme or any of seven vertical whitespace
characters. Good for dealing with textfiles coming from different operating systems.
\R
s/\R/\n/g; # normalize all linebreaks to \n
℞23:Getcharactercategory
Find the general category of a numeric codepoint.
use Unicode::UCD qw(charinfo);
my $cat = charinfo(0x3A3)->{category}; # "Lu"
℞24:DisablingUnicode-awarenessinbuiltincharclasses
Disable "\w", "\b", "\s", "\d", and the POSIX classes from working correctly on Unicode either in this
scope, or in just one regex.
use v5.14;
use re "/a";
# OR
my($num) = $str =~ /(\d+)/a;
Or use specific un-Unicode properties, like "\p{ahex}" and "\p{POSIX_Digit"}. Properties still work
normally no matter what charset modifiers ("/d /u /l /a /aa") should be effect.
℞25:MatchUnicodepropertiesinregexwith\p,\P
These all match a single codepoint with the given property. Use "\P" in place of "\p" to match one
codepoint lacking that property.
\pL, \pN, \pS, \pP, \pM, \pZ, \pC
\p{Sk}, \p{Ps}, \p{Lt}
\p{alpha}, \p{upper}, \p{lower}
\p{Latin}, \p{Greek}
\p{script_extensions=Latin}, \p{scx=Greek}
\p{East_Asian_Width=Wide}, \p{EA=W}
\p{Line_Break=Hyphen}, \p{LB=HY}
\p{Numeric_Value=4}, \p{NV=4}
℞26:Customcharacterproperties
Define at compile-time your own custom character properties for use in regexes.
# using private-use characters
sub In_Tengwar { "E000\tE07F\n" }
if (/\p{In_Tengwar}/) { ... }
# blending existing properties
sub Is_GraecoRoman_Title {<<'END_OF_SET'}
+utf8::IsLatin
+utf8::IsGreek
&utf8::IsTitle
END_OF_SET
if (/\p{Is_GraecoRoman_Title}/ { ... }
℞27:Unicodenormalization
Typically render into NFD on input and NFC on output. Using NFKC or NFKD functions improves recall on
searches, assuming you've already done to the same text to be searched. Note that this is about much more
than just pre- combined compatibility glyphs; it also reorders marks according to their canonical
combining classes and weeds out singletons.
use Unicode::Normalize;
my $nfd = NFD($orig);
my $nfc = NFC($orig);
my $nfkd = NFKD($orig);
my $nfkc = NFKC($orig);
℞28:Convertnon-ASCIIUnicodenumerics
Unless you’ve used "/a" or "/aa", "\d" matches more than ASCII digits only, but Perl’s implicit string-
to-number conversion does not current recognize these. Here’s how to convert such strings manually.
use v5.14; # needed for num() function
use Unicode::UCD qw(num);
my $str = "got Ⅻ and ४५६७ and ⅞ and here";
my @nums = ();
while ($str =~ /(\d+|\N)/g) { # not just ASCII!
push @nums, num($1);
}
say "@nums"; # 12 4567 0.875
use charnames qw(:full);
my $nv = num("\N{RUMI DIGIT ONE}\N{RUMI DIGIT TWO}");
℞29:MatchUnicodegraphemeclusterinregex
Programmer-visible “characters” are codepoints matched by "/./s", but user-visible “characters” are
graphemes matched by "/\X/".
# Find vowel *plus* any combining diacritics,underlining,etc.
my $nfd = NFD($orig);
$nfd =~ / (?=[aeiou]) \X /xi
℞30:Extractbygraphemeinsteadofbycodepoint(regex)
# match and grab five first graphemes
my($first_five) = $str =~ /^ ( \X{5} ) /x;
℞31:Extractbygraphemeinsteadofbycodepoint(substr)
# cpan -i Unicode::GCString
use Unicode::GCString;
my $gcs = Unicode::GCString->new($str);
my $first_five = $gcs->substr(0, 5);
℞32:Reversestringbygrapheme
Reversing by codepoint messes up diacritics, mistakenly converting "crème brûlée" into "éel̂urb em̀erc"
instead of into "eélûrb emèrc"; so reverse by grapheme instead. Both these approaches work right no
matter what normalization the string is in:
$str = join("", reverse $str =~ /\X/g);
# OR: cpan -i Unicode::GCString
use Unicode::GCString;
$str = reverse Unicode::GCString->new($str);
℞33:Stringlengthingraphemes
The string "brûlée" has six graphemes but up to eight codepoints. This counts by grapheme, not by
codepoint:
my $str = "brûlée";
my $count = 0;
while ($str =~ /\X/g) { $count++ }
# OR: cpan -i Unicode::GCString
use Unicode::GCString;
my $gcs = Unicode::GCString->new($str);
my $count = $gcs->length;
℞34:Unicodecolumn-widthforprinting
Perl’s "printf", "sprintf", and "format" think all codepoints take up 1 print column, but many take 0 or
2. Here to show that normalization makes no difference, we print out both forms:
use Unicode::GCString;
use Unicode::Normalize;
my @words = qw/crème brûlée/;
@words = map { NFC($_), NFD($_) } @words;
for my $str (@words) {
my $gcs = Unicode::GCString->new($str);
my $cols = $gcs->columns;
my $pad = " " x (10 - $cols);
say str, $pad, " |";
}
generates this to show that it pads correctly no matter the normalization:
crème |
crème |
brûlée |
brûlée |
℞35:Unicodecollation
Text sorted by numeric codepoint follows no reasonable alphabetic order; use the UCA for sorting text.
use Unicode::Collate;
my $col = Unicode::Collate->new();
my @list = $col->sort(@old_list);
See the ucsort program from the Unicode::Tussle CPAN module for a convenient command-line interface to
this module.
℞36:Case-andaccent-insensitiveUnicodesort
Specify a collation strength of level 1 to ignore case and diacritics, only looking at the basic
character.
use Unicode::Collate;
my $col = Unicode::Collate->new(level => 1);
my @list = $col->sort(@old_list);
℞37:Unicodelocalecollation
Some locales have special sorting rules.
# either use v5.12, OR: cpan -i Unicode::Collate::Locale
use Unicode::Collate::Locale;
my $col = Unicode::Collate::Locale->new(locale => "de__phonebook");
my @list = $col->sort(@old_list);
The ucsort program mentioned above accepts a "--locale" parameter.
℞38:Making"cmp"workontextinsteadofcodepoints
Instead of this:
@srecs = sort {
$b->{AGE} <=> $a->{AGE}
||
$a->{NAME} cmp $b->{NAME}
} @recs;
Use this:
my $coll = Unicode::Collate->new();
for my $rec (@recs) {
$rec->{NAME_key} = $coll->getSortKey( $rec->{NAME} );
}
@srecs = sort {
$b->{AGE} <=> $a->{AGE}
||
$a->{NAME_key} cmp $b->{NAME_key}
} @recs;
℞39:Case-andaccent-insensitivecomparisons
Use a collator object to compare Unicode text by character instead of by codepoint.
use Unicode::Collate;
my $es = Unicode::Collate->new(
level => 1,
normalization => undef
);
# now both are true:
$es->eq("García", "GARCIA" );
$es->eq("Márquez", "MARQUEZ");
℞40:Case-andaccent-insensitivelocalecomparisons
Same, but in a specific locale.
my $de = Unicode::Collate::Locale->new(
locale => "de__phonebook",
);
# now this is true:
$de->eq("tschüß", "TSCHUESS"); # notice ü => UE, ß => SS
℞41:Unicodelinebreaking
Break up text into lines according to Unicode rules.
# cpan -i Unicode::LineBreak
use Unicode::LineBreak;
use charnames qw(:full);
my $para = "This is a super\N{HYPHEN}long string. " x 20;
my $fmt = Unicode::LineBreak->new;
print $fmt->break($para), "\n";
℞42:UnicodetextinDBMhashes,thetediousway
Using a regular Perl string as a key or value for a DBM hash will trigger a wide character exception if
any codepoints won’t fit into a byte. Here’s how to manually manage the translation:
use DB_File;
use Encode qw(encode decode);
tie %dbhash, "DB_File", "pathname";
# STORE
# assume $uni_key and $uni_value are abstract Unicode strings
my $enc_key = encode("UTF-8", $uni_key, 1);
my $enc_value = encode("UTF-8", $uni_value, 1);
$dbhash{$enc_key} = $enc_value;
# FETCH
# assume $uni_key holds a normal Perl string (abstract Unicode)
my $enc_key = encode("UTF-8", $uni_key, 1);
my $enc_value = $dbhash{$enc_key};
my $uni_value = decode("UTF-8", $enc_value, 1);
℞43:UnicodetextinDBMhashes,theeasyway
Here’s how to implicitly manage the translation; all encoding and decoding is done automatically, just as
with streams that have a particular encoding attached to them:
use DB_File;
use DBM_Filter;
my $dbobj = tie %dbhash, "DB_File", "pathname";
$dbobj->Filter_Value("utf8"); # this is the magic bit
# STORE
# assume $uni_key and $uni_value are abstract Unicode strings
$dbhash{$uni_key} = $uni_value;
# FETCH
# $uni_key holds a normal Perl string (abstract Unicode)
my $uni_value = $dbhash{$uni_key};
℞44:PROGRAM:DemoofUnicodecollationandprinting
Here’s a full program showing how to make use of locale-sensitive sorting, Unicode casing, and managing
print widths when some of the characters take up zero or two columns, not just one column each time.
When run, the following program produces this nicely aligned output:
Crème Brûlée....... €2.00
Éclair............. €1.60
Fideuà............. €4.20
Hamburger.......... €6.00
Jamón Serrano...... €4.45
Linguiça........... €7.00
Pâté............... €4.15
Pears.............. €2.00
Pêches............. €2.25
Smørbrød........... €5.75
Spätzle............ €5.50
Xoriço............. €3.00
Γύρος.............. €6.50
막걸리............. €4.00
おもち............. €2.65
お好み焼き......... €8.00
シュークリーム..... €1.85
寿司............... €9.99
包子............... €7.50
Here's that program.
#!/usr/bin/env perl
# umenu - demo sorting and printing of Unicode food
#
# (obligatory and increasingly long preamble)
#
use v5.36;
use utf8;
use warnings qw(FATAL utf8); # fatalize encoding faults
use open qw(:std :encoding(UTF-8)); # undeclared streams in UTF-8
use charnames qw(:full :short); # unneeded in v5.16
# std modules
use Unicode::Normalize; # std perl distro as of v5.8
use List::Util qw(max); # std perl distro as of v5.10
use Unicode::Collate::Locale; # std perl distro as of v5.14
# cpan modules
use Unicode::GCString; # from CPAN
my %price = (
"γύρος" => 6.50, # gyros
"pears" => 2.00, # like um, pears
"linguiça" => 7.00, # spicy sausage, Portuguese
"xoriço" => 3.00, # chorizo sausage, Catalan
"hamburger" => 6.00, # burgermeister meisterburger
"éclair" => 1.60, # dessert, French
"smørbrød" => 5.75, # sandwiches, Norwegian
"spätzle" => 5.50, # Bayerisch noodles, little sparrows
"包子" => 7.50, # bao1 zi5, steamed pork buns, Mandarin
"jamón serrano" => 4.45, # country ham, Spanish
"pêches" => 2.25, # peaches, French
"シュークリーム" => 1.85, # cream-filled pastry like eclair
"막걸리" => 4.00, # makgeolli, Korean rice wine
"寿司" => 9.99, # sushi, Japanese
"おもち" => 2.65, # omochi, rice cakes, Japanese
"crème brûlée" => 2.00, # crema catalana
"fideuà" => 4.20, # more noodles, Valencian
# (Catalan=fideuada)
"pâté" => 4.15, # gooseliver paste, French
"お好み焼き" => 8.00, # okonomiyaki, Japanese
);
my $width = 5 + max map { colwidth($_) } keys %price;
# So the Asian stuff comes out in an order that someone
# who reads those scripts won't freak out over; the
# CJK stuff will be in JIS X 0208 order that way.
my $coll = Unicode::Collate::Locale->new(locale => "ja");
for my $item ($coll->sort(keys %price)) {
print pad(entitle($item), $width, ".");
printf " €%.2f\n", $price{$item};
}
sub pad ($str, $width, $padchar) {
return $str . ($padchar x ($width - colwidth($str)));
}
sub colwidth ($str) {
return Unicode::GCString->new($str)->columns;
}
sub entitle ($str) {
$str =~ s{ (?=\pL)(\S) (\S*) }
{ ucfirst($1) . lc($2) }xge;
return $str;
}
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