3 $utf8::hint_bits = 0x00800000;
8 $^H |= $utf8::hint_bits;
9 $enc{caller()} = $_[1] if $_[1];
13 $^H &= ~$utf8::hint_bits;
17 require "utf8_heavy.pl";
18 goto &$AUTOLOAD if defined &$AUTOLOAD;
20 Carp::croak("Undefined subroutine $AUTOLOAD called");
28 utf8 - Perl pragma to enable/disable UTF-8 (or UTF-EBCDIC) in source code
35 # Convert a Perl scalar to/from UTF-8.
36 $num_octets = utf8::upgrade($string);
37 $success = utf8::downgrade($string[, FAIL_OK]);
39 # Change the native bytes of a Perl scalar to/from UTF-8 bytes.
40 utf8::encode($string);
41 utf8::decode($string);
43 $flag = utf8::is_utf8(STRING); # since Perl 5.8.1
44 $flag = utf8::valid(STRING);
48 The C<use utf8> pragma tells the Perl parser to allow UTF-8 in the
49 program text in the current lexical scope (allow UTF-EBCDIC on EBCDIC based
50 platforms). The C<no utf8> pragma tells Perl to switch back to treating
51 the source text as literal bytes in the current lexical scope.
53 This pragma is primarily a compatibility device. Perl versions
54 earlier than 5.6 allowed arbitrary bytes in source code, whereas
55 in future we would like to standardize on the UTF-8 encoding for
58 B<Do not use this pragma for anything else than telling Perl that your
59 script is written in UTF-8.> The utility functions described below are
60 useful for their own purposes, but they are not really part of the
63 Until UTF-8 becomes the default format for source text, either this
64 pragma or the L<encoding> pragma should be used to recognize UTF-8
65 in the source. When UTF-8 becomes the standard source format, this
66 pragma will effectively become a no-op. For convenience in what
67 follows the term I<UTF-X> is used to refer to UTF-8 on ASCII and ISO
68 Latin based platforms and UTF-EBCDIC on EBCDIC based platforms.
70 See also the effects of the C<-C> switch and its cousin, the
71 C<$ENV{PERL_UNICODE}>, in L<perlrun>.
73 Enabling the C<utf8> pragma has the following effect:
79 Bytes in the source text that have their high-bit set will be treated
80 as being part of a literal UTF-X sequence. This includes most
81 literals such as identifier names, string constants, and constant
82 regular expression patterns.
84 On EBCDIC platforms characters in the Latin 1 character set are
85 treated as being part of a literal UTF-EBCDIC character.
89 Note that if you have bytes with the eighth bit on in your script
90 (for example embedded Latin-1 in your string literals), C<use utf8>
91 will be unhappy since the bytes are most probably not well-formed
92 UTF-X. If you want to have such bytes under C<use utf8>, you can disable
93 this pragma until the end the block (or file, if at top level) by
96 If you want to automatically upgrade your 8-bit legacy bytes to Unicode,
97 use the L<encoding> pragma instead of this pragma. For example, if
98 you want to implicitly upgrade your ISO 8859-1 (Latin-1) bytes to Unicode
99 as used in e.g. C<chr()> and C<\x{...}>, try this:
101 use encoding "latin-1";
105 In case you are wondering: C<use encoding 'utf8';> is mostly the same as
106 C<use utf8;>, except that C<use encoding> marks all string literals in the
107 source code as Unicode, regardless of whether they contain any high-bit bytes.
108 Moreover, C<use encoding> installs IO layers on C<STDIN> and C<STDOUT> to work
109 with Unicode strings; see L<encoding> for details.
111 =head2 Utility functions
113 The following functions are defined in the C<utf8::> package by the
114 Perl core. You do not need to say C<use utf8> to use these and in fact
115 you should not say that unless you really want to have UTF-8 source code.
119 =item * $num_octets = utf8::upgrade($string)
121 Converts in-place the octet sequence in the native encoding
122 (Latin-1 or EBCDIC) to the equivalent character sequence in I<UTF-X>.
123 I<$string> already encoded as characters does no harm.
124 Returns the number of octets necessary to represent the string as I<UTF-X>.
125 Can be used to make sure that the UTF-8 flag is on,
126 so that C<\w> or C<lc()> work as Unicode on strings
127 containing characters in the range 0x80-0xFF (on ASCII and
130 B<Note that this function does not handle arbitrary encodings.>
131 Therefore I<Encode.pm> is recommended for the general purposes.
133 Affected by the encoding pragma.
135 =item * $success = utf8::downgrade($string[, FAIL_OK])
137 Converts in-place the character sequence in I<UTF-X>
138 to the equivalent octet sequence in the native encoding (Latin-1 or EBCDIC).
139 I<$string> already encoded as octets does no harm.
140 Returns true on success. On failure dies or, if the value of
141 C<FAIL_OK> is true, returns false.
142 Can be used to make sure that the UTF-8 flag is off,
143 e.g. when you want to make sure that the substr() or length() function
144 works with the usually faster byte algorithm.
146 B<Note that this function does not handle arbitrary encodings.>
147 Therefore I<Encode.pm> is recommended for the general purposes.
149 B<Not> affected by the encoding pragma.
151 B<NOTE:> this function is experimental and may change
152 or be removed without notice.
154 =item * utf8::encode($string)
156 Converts in-place the character sequence to the corresponding octet sequence
157 in I<UTF-X>. The UTF-8 flag is turned off. Returns nothing.
159 B<Note that this function does not handle arbitrary encodings.>
160 Therefore I<Encode.pm> is recommended for the general purposes.
162 =item * utf8::decode($string)
164 Attempts to convert in-place the octet sequence in I<UTF-X>
165 to the corresponding character sequence. The UTF-8 flag is turned on
166 only if the source string contains multiple-byte I<UTF-X> characters.
167 If I<$string> is invalid as I<UTF-X>, returns false; otherwise returns true.
169 B<Note that this function does not handle arbitrary encodings.>
170 Therefore I<Encode.pm> is recommended for the general purposes.
172 B<NOTE:> this function is experimental and may change
173 or be removed without notice.
175 =item * $flag = utf8::is_utf8(STRING)
177 (Since Perl 5.8.1) Test whether STRING is in UTF-8. Functionally
178 the same as Encode::is_utf8().
180 =item * $flag = utf8::valid(STRING)
182 [INTERNAL] Test whether STRING is in a consistent state regarding
183 UTF-8. Will return true is well-formed UTF-8 and has the UTF-8 flag
184 on B<or> if string is held as bytes (both these states are 'consistent').
185 Main reason for this routine is to allow Perl's testsuite to check
186 that operations have left strings in a consistent state. You most
187 probably want to use utf8::is_utf8() instead.
191 C<utf8::encode> is like C<utf8::upgrade>, but the UTF8 flag is
192 cleared. See L<perlunicode> for more on the UTF8 flag and the C API
193 functions C<sv_utf8_upgrade>, C<sv_utf8_downgrade>, C<sv_utf8_encode>,
194 and C<sv_utf8_decode>, which are wrapped by the Perl functions
195 C<utf8::upgrade>, C<utf8::downgrade>, C<utf8::encode> and
196 C<utf8::decode>. Note that in the Perl 5.8.0 and 5.8.1 implementation
197 the functions utf8::is_utf8, utf8::valid, utf8::encode, utf8::decode,
198 utf8::upgrade, and utf8::downgrade are always available, without a
199 C<require utf8> statement-- this may change in future releases.
203 One can have Unicode in identifier names, but not in package/class or
204 subroutine names. While some limited functionality towards this does
205 exist as of Perl 5.8.0, that is more accidental than designed; use of
206 Unicode for the said purposes is unsupported.
208 One reason of this unfinishedness is its (currently) inherent
209 unportability: since both package names and subroutine names may need
210 to be mapped to file and directory names, the Unicode capability of
211 the filesystem becomes important-- and there unfortunately aren't
216 L<perluniintro>, L<encoding>, L<perlrun>, L<bytes>, L<perlunicode>