man
utf8 encoding
utf8(3pm) Perl Programmers Reference Guide utf8(3pm)
NAME
utf8 - Perl pragma to enable/disable UTF-8 (or UTF-EBCDIC) in source
code
SYNOPSIS
use utf8;
no utf8;
# Convert the internal representation of a Perl scalar to/from UTF-8.
$num_octets = utf8::upgrade($string);
$success = utf8::downgrade($string[, $fail_ok]);
# Change each character of a Perl scalar to/from a series of
# characters that represent the UTF-8 bytes of each original character.
utf8::encode($string); # "\x{100}" becomes "\xc4\x80"
utf8::decode($string); # "\xc4\x80" becomes "\x{100}"
# Convert a code point from the platform native character set to
# Unicode, and vice-versa.
$unicode = utf8::native_to_unicode(ord('A')); # returns 65 on both
# ASCII and EBCDIC
# platforms
$native = utf8::unicode_to_native(65); # returns 65 on ASCII
# platforms; 193 on
# EBCDIC
$flag = utf8::is_utf8($string); # since Perl 5.8.1
$flag = utf8::valid($string);
DESCRIPTION
The "use utf8" pragma tells the Perl parser to allow UTF-8 in the
program text in the current lexical scope. The "no utf8" pragma tells
Perl to switch back to treating the source text as literal bytes in the
current lexical scope. (On EBCDIC platforms, technically it is
allowing UTF-EBCDIC, and not UTF-8, but this distinction is academic,
so in this document the term UTF-8 is used to mean both).
Do not use this pragma for anything else than telling Perl that your
script is written in UTF-8. The utility functions described below are
directly usable without "use utf8;".
Because it is not possible to reliably tell UTF-8 from native 8 bit
encodings, you need either a Byte Order Mark at the beginning of your
source code, or "use utf8;", to instruct perl.
When UTF-8 becomes the standard source format, this pragma will
effectively become a no-op.
See also the effects of the "-C" switch and its cousin, the
"PERL_UNICODE" environment variable, in perlrun.
Enabling the "utf8" pragma has the following effect:
o Bytes in the source text that are not in the ASCII character set
will be treated as being part of a literal UTF-8 sequence. This
includes most literals such as identifier names, string constants,
and constant regular expression patterns.
Note that if you have non-ASCII, non-UTF-8 bytes in your script (for
example embedded Latin-1 in your string literals), "use utf8" will be
unhappy. If you want to have such bytes under "use utf8", you can
disable this pragma until the end the block (or file, if at top level)
by "no utf8;".
Utility functions
The following functions are defined in the "utf8::" package by the Perl
core. You do not need to say "use utf8" to use these and in fact you
should not say that unless you really want to have UTF-8 source code.
o "$num_octets = utf8::upgrade($string)"
(Since Perl v5.8.0) Converts in-place the internal representation
of the string from an octet sequence in the native encoding
(Latin-1 or EBCDIC) to UTF-8. The logical character sequence itself
is unchanged. If $string is already upgraded, then this is a no-
op. Returns the number of octets necessary to represent the string
as UTF-8.
If your code needs to be compatible with versions of perl without
"use feature 'unicode_strings';", you can force Unicode semantics
on a given string:
# force unicode semantics for $string without the
# "unicode_strings" feature
utf8::upgrade($string);
For example:
# without explicit or implicit use feature 'unicode_strings'
my $x = "\xDF"; # LATIN SMALL LETTER SHARP S
$x =~ /ss/i; # won't match
my $y = uc($x); # won't convert
utf8::upgrade($x);
$x =~ /ss/i; # matches
my $z = uc($x); # converts to "SS"
Note that this function does not handle arbitrary encodings; use
Encode instead.
o "$success = utf8::downgrade($string[, $fail_ok])"
(Since Perl v5.8.0) Converts in-place the internal representation
of the string from UTF-8 to the equivalent octet sequence in the
native encoding (Latin-1 or EBCDIC). The logical character sequence
itself is unchanged. If $string is already stored as native 8 bit,
then this is a no-op. Can be used to make sure that the UTF-8 flag
is off, e.g. when you want to make sure that the substr() or
length() function works with the usually faster byte algorithm.
Fails if the original UTF-8 sequence cannot be represented in the
native 8 bit encoding. On failure dies or, if the value of $fail_ok
is true, returns false.
Returns true on success.
If your code expects an octet sequence this can be used to validate
that you've received one:
# throw an exception if not representable as octets
utf8::downgrade($string)
# or do your own error handling
utf8::downgrade($string, 1) or die "string must be octets";
Note that this function does not handle arbitrary encodings; use
Encode instead.
o "utf8::encode($string)"
(Since Perl v5.8.0) Converts in-place the character sequence to the
corresponding octet sequence in Perl's extended UTF-8. That is,
every (possibly wide) character gets replaced with a sequence of
one or more characters that represent the individual UTF-8 bytes of
the character. The UTF8 flag is turned off. Returns nothing.
my $x = "\x{100}"; # $x contains one character, with ord 0x100
utf8::encode($x); # $x contains two characters, with ords (on
# ASCII platforms) 0xc4 and 0x80. On EBCDIC
# 1047, this would instead be 0x8C and 0x41.
Similar to:
use Encode;
$x = Encode::encode("utf8", $x);
Note that this function does not handle arbitrary encodings; use
Encode instead.
o "$success = utf8::decode($string)"
(Since Perl v5.8.0) Attempts to convert in-place the octet sequence
encoded in Perl's extended UTF-8 to the corresponding character
sequence. That is, it replaces each sequence of characters in the
string whose ords represent a valid (extended) UTF-8 byte sequence,
with the corresponding single character. The UTF-8 flag is turned
on only if the source string contains multiple-byte UTF-8
characters. If $string is invalid as extended UTF-8, returns
false; otherwise returns true.
my $x = "\xc4\x80"; # $x contains two characters, with ords
# 0xc4 and 0x80
utf8::decode($x); # On ASCII platforms, $x contains one char,
# with ord 0x100. Since these bytes aren't
# legal UTF-EBCDIC, on EBCDIC platforms, $x is
# unchanged and the function returns FALSE.
Note that this function does not handle arbitrary encodings; use
Encode instead.
o "$unicode = utf8::native_to_unicode($code_point)"
(Since Perl v5.8.0) This takes an unsigned integer (which
represents the ordinal number of a character (or a code point) on
the platform the program is being run on) and returns its Unicode
equivalent value. Since ASCII platforms natively use the Unicode
code points, this function returns its input on them. On EBCDIC
platforms it converts from EBCDIC to Unicode.
A meaningless value will currently be returned if the input is not
an unsigned integer.
Since Perl v5.22.0, calls to this function are optimized out on
ASCII platforms, so there is no performance hit in using it there.
o "$native = utf8::unicode_to_native($code_point)"
(Since Perl v5.8.0) This is the inverse of
"utf8::native_to_unicode()", converting the other direction.
Again, on ASCII platforms, this returns its input, but on EBCDIC
platforms it will find the native platform code point, given any
Unicode one.
A meaningless value will currently be returned if the input is not
an unsigned integer.
Since Perl v5.22.0, calls to this function are optimized out on
ASCII platforms, so there is no performance hit in using it there.
o "$flag = utf8::is_utf8($string)"
(Since Perl 5.8.1) Test whether $string is marked internally as
encoded in UTF-8. Functionally the same as
"Encode::is_utf8($string)".
Typically only necessary for debugging and testing, if you need to
dump the internals of an SV, Devel::Peek's Dump() provides more
detail in a compact form.
If you still think you need this outside of debugging, testing or
dealing with filenames, you should probably read perlunitut and
"What is "the UTF8 flag"?" in perlunifaq.
Don't use this flag as a marker to distinguish character and binary
data: that should be decided for each variable when you write your
code.
To force unicode semantics in code portable to perl 5.8 and 5.10,
call "utf8::upgrade($string)" unconditionally.
o "$flag = utf8::valid($string)"
[INTERNAL] Test whether $string is in a consistent state regarding
UTF-8. Will return true if it is well-formed Perl extended UTF-8
and has the UTF-8 flag on or if $string is held as bytes (both
these states are 'consistent'). The main reason for this routine
is to allow Perl's test suite to check that operations have left
strings in a consistent state.
"utf8::encode" is like "utf8::upgrade", but the UTF8 flag is cleared.
See perlunicode, and the C API functions "sv_utf8_upgrade",
""sv_utf8_downgrade" in perlapi", ""sv_utf8_encode" in perlapi", and
""sv_utf8_decode" in perlapi", which are wrapped by the Perl functions
"utf8::upgrade", "utf8::downgrade", "utf8::encode" and "utf8::decode".
Also, the functions "utf8::is_utf8", "utf8::valid", "utf8::encode",
"utf8::decode", "utf8::upgrade", and "utf8::downgrade" are actually
internal, and thus always available, without a "require utf8"
statement.
BUGS
Some filesystems may not support UTF-8 file names, or they may be
supported incompatibly with Perl. Therefore UTF-8 names that are
visible to the filesystem, such as module names may not work.
SEE ALSO
perlunitut, perluniintro, perlrun, bytes, perlunicode
perl v5.32.1 2025-07-03 utf8(3pm)
encoding(3) User Contributed Perl Documentation encoding(3)
NAME
encoding - allows you to write your script in non-ASCII and non-UTF-8
WARNING
This module has been deprecated since perl v5.18. See "DESCRIPTION"
and "BUGS".
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
no encoding;
# an alternate way, Filter
use encoding "euc-jp", Filter=>1;
# now you can use kanji identifiers -- in euc-jp!
# encode based on the current locale - specialized purposes only;
# fraught with danger!!
use encoding ':locale';
DESCRIPTION
This pragma is used to enable a Perl script to be written in encodings
that aren't strictly ASCII nor UTF-8. It translates all or portions of
the Perl program script from a given encoding into UTF-8, and changes
the PerlIO layers of "STDIN" and "STDOUT" to the encoding specified.
This pragma dates from the days when UTF-8-enabled editors were
uncommon. But that was long ago, and the need for it is greatly
diminished. That, coupled with the fact that it doesn't work with
threads, along with other problems, (see "BUGS") have led to its being
deprecated. It is planned to remove this pragma in a future Perl
version. New code should be written in UTF-8, and the "use utf8"
pragma used instead (see perluniintro and utf8 for details). Old code
should be converted to UTF-8, via something like the recipe in the
"SYNOPSIS" (though this simple approach may require manual adjustments
afterwards).
If UTF-8 is not an option, it is recommended that one use a simple
source filter, such as that provided by Filter::Encoding on CPAN or
this pragma's own "Filter" option (see below).
The only legitimate use of this pragma is almost certainly just one per
file, near the top, with file scope, as the file is likely going to
only be written in one encoding. Further restrictions apply in Perls
before v5.22 (see "Prior to Perl v5.22").
There are two basic modes of operation (plus turning if off):
"use encoding ['ENCNAME'] ;"
Please note: This mode of operation is no longer supported as of
Perl v5.26.
This is the normal operation. It translates various literals
encountered in the Perl source file from the encoding ENCNAME into
UTF-8, and similarly converts character code points. This is used
when the script is a combination of ASCII (for the variable names
and punctuation, etc), but the literal data is in the specified
encoding.
ENCNAME is optional. If omitted, the encoding specified in the
environment variable "PERL_ENCODING" is used. If this isn't set,
or the resolved-to encoding is not known to "Encode", the error
"Unknown encoding 'ENCNAME'" will be thrown.
Starting in Perl v5.8.6 ("Encode" version 2.0.1), ENCNAME may be
the name ":locale". This is for very specialized applications, and
is documented in "The ":locale" sub-pragma" below.
The literals that are converted are "q//, qq//, qr//, qw///, qx//",
and starting in v5.8.1, "tr///". Operations that do conversions
include "chr", "ord", "utf8::upgrade" (but not "utf8::downgrade"),
and "chomp".
Also starting in v5.8.1, the "DATA" pseudo-filehandle is translated
from the encoding into UTF-8.
For example, 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
that code in UTF-8:
my $Rakuda = "\x{99F1}\x{99DD}"; # two Unicode Characters
s/\bCamel\b/$Rakuda/;
See "EXAMPLE" below for a more complete example.
Unless "${^UNICODE}" (available starting in v5.8.2) exists and is
non-zero, the PerlIO layers of "STDIN" and "STDOUT" are set to
"":encoding(ENCNAME)"". 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.
Note that "STDERR" WILL NOT be changed, regardless.
Also note that non-STD file handles remain unaffected. Use "use
open" or "binmode" to change the layers of those.
"use encoding ENCNAME, Filter=>1;"
This operates as above, but the "Filter" argument with a non-zero
value causes the entire script, and not just literals, to be
translated from the encoding into UTF-8. This allows identifiers
in the source to be in that encoding as well. (Problems may occur
if the encoding is not a superset of ASCII; imagine all your semi-
colons being translated into something different.) One can use
this form to make
${"\x{4eba}"}++
work. (This is equivalent to "$human++", where human is a single
Han ideograph).
This effectively means that your source code behaves as if it were
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.".
This option is significantly slower than the other one.
"no encoding;"
Unsets the script encoding. The layers of "STDIN", "STDOUT" are
reset to "":raw"" (the default unprocessed raw stream of bytes).
OPTIONS
Setting "STDIN" and/or "STDOUT" individually
The encodings of "STDIN" and "STDOUT" are individually settable by
parameters to the pragma:
use encoding 'euc-tw', STDIN => 'greek' ...;
In this case, you cannot omit the first ENCNAME. "STDIN => undef"
turns the I/O transcoding completely off for that filehandle.
When "${^UNICODE}" (available starting in v5.8.2) exists and is non-
zero, these options will be completely ignored. See ""${^UNICODE}"" in
perlvar and ""-C"" in perlrun for details.
The ":locale" sub-pragma
Starting in v5.8.6, the encoding name may be ":locale". This means
that the encoding is taken from the current locale, and not hard-coded
by the pragma. Since a script really can only be encoded in exactly
one encoding, this option is dangerous. It makes sense only if the
script itself is written in ASCII, and all the possible locales that
will be in use when the script is executed are supersets of ASCII.
That means that the script itself doesn't get changed, but the I/O
handles have the specified encoding added, and the operations like
"chr" and "ord" use that encoding.
The logic of finding which locale ":locale" uses 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.
CAVEATS
SIDE EFFECTS
o If the "encoding" pragma is in scope then the lengths returned are
calculated from the length of $/ in Unicode characters, which is
not always the same as the length of $/ in the native encoding.
o Without this pragma, 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.
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
\x{100}\xDF
\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.
Prior to Perl v5.22
The pragma was a per script, not a per block lexical. Only the last
"use encoding" or "no encoding" mattered, and it affected the whole
script. However, the "no encoding" pragma was supported and "use
encoding" could appear as many times as you want in a given script
(though only the last was effective).
Since the scope wasn't lexical, other modules' use of "chr", "ord",
etc. were affected. This leads to spooky, incorrect action at a
distance that is hard to debug.
This means you would have to be very careful of the load order:
# 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";
Prior to Encode version 1.87
o "STDIN" and "STDOUT" were not set under the filter option. And
"STDIN=>ENCODING" and "STDOUT=>ENCODING" didn't work like non-
filter version.
o "use utf8" wasn't implicitly declared so you have to "use utf8" to
do
${"\x{4eba}"}++
Prior to Perl v5.8.1
"NON-EUC" doublebyte encodings
Because perl needs to parse the script before applying this pragma,
such encodings as Shift_JIS and Big-5 that may contain '\'
(BACKSLASH; "\x5c") in the second byte fail because the second byte
may accidentally escape the quoting character that follows.
"tr///"
The encoding pragma works by decoding string literals in
"q//,qq//,qr//,qw///, qx//" and so forth. In perl v5.8.0, 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
$kana =~ tr/\x{3041}-\x{3093}/\x{30a1}-\x{30f3}/;
Legend of characters above
utf8 euc-jp charnames::viacode()
-----------------------------------------
\x{3041} \xA4\xA1 HIRAGANA LETTER SMALL A
\x{3093} \xA4\xF3 HIRAGANA LETTER N
\x{30a1} \xA5\xA1 KATAKANA LETTER SMALL A
\x{30f3} \xA5\xF3 KATAKANA LETTER N
This counterintuitive behavior has been fixed in perl v5.8.1.
In perl v5.8.0, you can work around this as follows;
use encoding 'euc-jp';
# ....
eval qq{ \$kana =~ tr/\xA4\xA1-\xA4\xF3/\xA5\xA1-\xA5\xF3/ };
Note the "tr//" expression is surrounded by "qq{}". The idea
behind this is the same as the classic idiom that makes "tr///"
'interpolate':
tr/$from/$to/; # wrong!
eval qq{ tr/$from/$to/ }; # workaround.
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;
BUGS
Thread safety
"use encoding ..." is not thread-safe (i.e., do not use in threaded
applications).
Can't be used by more than one module in a single program.
Only one encoding is allowed. If you combine modules in a program
that have different encodings, only one will be actually used.
Other modules using "STDIN" and "STDOUT" get the encoded stream
They may be expecting something completely different.
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.
"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
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).
See also "CAVEATS"
HISTORY
This pragma first appeared in Perl v5.8.0. It has been enhanced in
later releases as specified above.
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
perl v5.32.1 2021-08-10 encoding(3)