utf8(3perl)

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version 5.44.0 · 14 versions
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💖 utf8(3perl) — Perl Programmers Reference Guide 💖

okay bestie, buckle up, this is the page about utf8, the pragma that lets you tell Perl "hey girl, my source code is written in UTF-8, pls respect it" 🦋

✨ 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);

like, look at that synopsis, it's giving "I contain multitudes" 💅

👑 DESCRIPTION 👑

okay so, the use utf8 pragma tells the Perl parser to allow UTF-8 in the program text in the current lexical scope. and then no utf8 tells Perl to switch back to treating the source text as literal bytes in the current lexical scope. 🎀

and yes, on EBCDIC platforms it's technically allowing UTF-EBCDIC and not UTF-8, but honestly that distinction is academic, so in this whole document the term UTF-8 is used to mean both. periodt 💫

bestie, real talk: do NOT use this pragma for literally anything else other than telling Perl that your script is written in UTF-8. the utility functions described below are directly usable without use utf8;. no cap.

and here's why you can't just vibe your way through it: 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. iconic, but also kind of a moment of silence 🫶

also go look at the effects of the -C switch and its cousin, the PERL_UNICODE environment variable, over in perlrun. iykyk ✨

Enabling the utf8 pragma has the following effect:

  • 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.

and lowkey a warning: 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 typing no utf8;. okurrr 🍓

🧚 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 really want to have UTF-8 source code. 💜

  • $num_octets = utf8::upgrade($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, bestie 👑. if $string is already upgraded, then this is a no-op. returns the number of octets necessary to represent the string as UTF-8. and since Perl v5.38, if $string is undef no action is taken; prior to that, it would be converted to be defined and zero-length. 📝

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"
heads up: note that this function does not handle arbitrary encodings; use Encode instead. 🙈
  • $success = utf8::downgrade($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 🔥.

it fails if the original UTF-8 sequence cannot be represented in the native 8 bit encoding 😭. on failure it 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($string, 1) or die "string must be octets";
again, note that this function does not handle arbitrary encodings; use Encode instead. 🌸
  • utf8::encode($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);
and like its siblings: note that this function does not handle arbitrary encodings; use Encode instead. 😭
  • $success = utf8::decode($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.
 my $y = "\xc3\x83\xc2\xab"; This has been encoded twice; this
                     # example is only for ASCII platforms
 utf8::decode($y);   # Converts $y to \xc3\xab, returns TRUE;
 utf8::decode($y);   # Further converts to \xeb, returns TRUE;
 utf8::decode($y);   # Returns FALSE, leaves $y unchanged
final reminder for this one, bestie: note that this function does not handle arbitrary encodings; use Encode instead. 🎀
  • $unicode = utf8::native_to_unicode($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. slay 💅

  • $native = utf8::unicode_to_native($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 either. 🎉

  • $flag = utf8::is_utf8($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. 📚

do NOT use this flag as a marker to distinguish character and binary data: that should be decided for each variable when you write your code. for real, it's not that girl. 🚫

to force unicode semantics in code portable to perl 5.8 and 5.10, call utf8::upgrade($string) unconditionally. ⭐

  • $flag = utf8::valid($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 😭

ok so bestie, plot twist time, because this is the part where we tell you what's lowkey broken and it's not even Perl's fault 💀

Some filesystems out there just straight up do not support UTF-8 file names, periodt. Like, they looked at your gorgeous multi-byte filename and said "no <3".

And worse: even when a filesystem does claim to support them, that support might be incompatible with Perl. So it's giving "yes queen" but then not actually functioning, which is the worst kind of betrayal fr fr 😭

So the consequence, and hear me out because this one matters: UTF-8 names that are visible to the filesystem — the classic example being module names — may just NOT WORK. 💅

⚠️ heads up: if your module names are full of pretty Unicode characters and things are mysteriously failing, the filesystem might be the hater in the situation, not you. 🫶

🦋 SEE ALSO 🦋

ok the girlies you should go read next, in no particular order because they're all iconic 👑

  • perlunitut — the tutorial bestie, start here if you're confused 🌸
  • perluniintro — the intro, for when you need the vibes explained first ✨
  • perlrun — all the command line stuff, the flags, the whole thing 🎀
  • bytes — the anti-UTF-8 energy, the pragma that says "no Unicode here" 🙈
  • perlunicode — the deep lore, the big one, the main character 👑

and that's the whole page bestie, you made it to the end 🥳 this was utf8(3perl) from perl v5.44.0, dated 2026-10-17 — go forth and encode responsibly, ily, mwah 💖🧚💜

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