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;
19 Carp::croak("Undefined subroutine $AUTOLOAD called");
27 utf8 - Perl pragma to enable/disable UTF-8 (or UTF-EBCDIC) in source code
34 # Convert a Perl scalar to/from UTF-8.
35 $num_octets = utf8::upgrade($string);
36 $success = utf8::downgrade($string[, FAIL_OK]);
38 # Change the native bytes of a Perl scalar to/from UTF-8 bytes.
39 utf8::encode($string);
40 utf8::decode($string);
42 $flag = utf8::is_utf8(STRING); # since Perl 5.8.1
43 $flag = utf8::valid(STRING);
47 The C<use utf8> pragma tells the Perl parser to allow UTF-8 in the
48 program text in the current lexical scope (allow UTF-EBCDIC on EBCDIC based
49 platforms). The C<no utf8> pragma tells Perl to switch back to treating
50 the source text as literal bytes in the current lexical scope.
52 This pragma is primarily a compatibility device. Perl versions
53 earlier than 5.6 allowed arbitrary bytes in source code, whereas
54 in future we would like to standardize on the UTF-8 encoding for
57 B<Do not use this pragma for anything else than telling Perl that your
58 script is written in UTF-8.> The utility functions described below are
59 useful for their own purposes, but they are not really part of the
62 Until UTF-8 becomes the default format for source text, either this
63 pragma or the L</encoding> pragma should be used to recognize UTF-8
64 in the source. When UTF-8 becomes the standard source format, this
65 pragma will effectively become a no-op. For convenience in what
66 follows the term I<UTF-X> is used to refer to UTF-8 on ASCII and ISO
67 Latin based platforms and UTF-EBCDIC on EBCDIC based platforms.
69 See also the effects of the C<-C> switch and its cousin, the
70 C<$ENV{PERL_UNICODE}>, in L<perlrun>.
72 Enabling the C<utf8> pragma has the following effect:
78 Bytes in the source text that have their high-bit set will be treated
79 as being part of a literal UTF-8 character. This includes most
80 literals such as identifier names, string constants, and constant
81 regular expression patterns.
83 On EBCDIC platforms characters in the Latin 1 character set are
84 treated as being part of a literal UTF-EBCDIC character.
88 Note that if you have bytes with the eighth bit on in your script
89 (for example embedded Latin-1 in your string literals), C<use utf8>
90 will be unhappy since the bytes are most probably not well-formed
91 UTF-8. If you want to have such bytes and use utf8, you can disable
92 utf8 until the end the block (or file, if at top level) by C<no utf8;>.
94 If you want to automatically upgrade your 8-bit legacy bytes to UTF-8,
95 use the L</encoding> pragma instead of this pragma. For example, if
96 you want to implicitly upgrade your ISO 8859-1 (Latin-1) bytes to UTF-8
97 as used in e.g. C<chr()> and C<\x{...}>, try this:
99 use encoding "latin-1";
103 In case you are wondering: yes, C<use encoding 'utf8';> works much
104 the same as C<use utf8;>.
106 =head2 Utility functions
108 The following functions are defined in the C<utf8::> package by the
109 Perl core. You do not need to say C<use utf8> to use these and in fact
110 you should not say that unless you really want to have UTF-8 source code.
114 =item * $num_octets = utf8::upgrade($string)
116 Converts in-place the octet sequence in the native encoding
117 (Latin-1 or EBCDIC) to the equivalent character sequence in I<UTF-X>.
118 I<$string> already encoded as characters does no harm.
119 Returns the number of octets necessary to represent the string as I<UTF-X>.
120 Can be used to make sure that the UTF-8 flag is on,
121 so that C<\w> or C<lc()> work as Unicode on strings
122 containing characters in the range 0x80-0xFF (on ASCII and
125 B<Note that this function does not handle arbitrary encodings.>
126 Therefore I<Encode.pm> is recommended for the general purposes.
128 Affected by the encoding pragma.
130 =item * $success = utf8::downgrade($string[, FAIL_OK])
132 Converts in-place the character sequence in I<UTF-X>
133 to the equivalent octet sequence in the native encoding (Latin-1 or EBCDIC).
134 I<$string> already encoded as octets does no harm.
135 Returns true on success. On failure dies or, if the value of
136 C<FAIL_OK> is true, returns false.
137 Can be used to make sure that the UTF-8 flag is off,
138 e.g. when you want to make sure that the substr() or length() function
139 works with the usually faster byte algorithm.
141 B<Note that this function does not handle arbitrary encodings.>
142 Therefore I<Encode.pm> is recommended for the general purposes.
144 B<Not> affected by the encoding pragma.
146 B<NOTE:> this function is experimental and may change
147 or be removed without notice.
149 =item * utf8::encode($string)
151 Converts in-place the character sequence to the corresponding octet sequence
152 in I<UTF-X>. The UTF-8 flag is turned off. Returns nothing.
154 B<Note that this function does not handle arbitrary encodings.>
155 Therefore I<Encode.pm> is recommended for the general purposes.
157 =item * utf8::decode($string)
159 Attempts to convert in-place the octet sequence in I<UTF-X>
160 to the corresponding character sequence. The UTF-8 flag is turned on
161 only if the source string contains multiple-byte I<UTF-X> characters.
162 If I<$string> is invalid as I<UTF-X>, returns false; otherwise returns true.
164 B<Note that this function does not handle arbitrary encodings.>
165 Therefore I<Encode.pm> is recommended for the general purposes.
167 B<NOTE:> this function is experimental and may change
168 or be removed without notice.
170 =item * $flag = utf8::is_utf8(STRING)
172 (Since Perl 5.8.1) Test whether STRING is in UTF-8. Functionally
173 the same as Encode::is_utf8().
175 =item * $flag = utf8::valid(STRING)
177 [INTERNAL] Test whether STRING is in a consistent state regarding
178 UTF-8. Will return true is well-formed UTF-8 and has the UTF-8 flag
179 on B<or> if string is held as bytes (both these states are 'consistent').
180 Main reason for this routine is to allow Perl's testsuite to check
181 that operations have left strings in a consistent state. You most
182 probably want to use utf8::is_utf8() instead.
186 C<utf8::encode> is like C<utf8::upgrade>, but the UTF8 flag is
187 cleared. See L<perlunicode> for more on the UTF8 flag and the C API
188 functions C<sv_utf8_upgrade>, C<sv_utf8_downgrade>, C<sv_utf8_encode>,
189 and C<sv_utf8_decode>, which are wrapped by the Perl functions
190 C<utf8::upgrade>, C<utf8::downgrade>, C<utf8::encode> and
191 C<utf8::decode>. Note that in the Perl 5.8.0 and 5.8.1 implementation
192 the functions utf8::is_utf8, utf8::valid, utf8::encode, utf8::decode,
193 utf8::upgrade, and utf8::downgrade are always available, without a
194 C<require utf8> statement-- this may change in future releases.
198 One can have Unicode in identifier names, but not in package/class or
199 subroutine names. While some limited functionality towards this does
200 exist as of Perl 5.8.0, that is more accidental than designed; use of
201 Unicode for the said purposes is unsupported.
203 One reason of this unfinishedness is its (currently) inherent
204 unportability: since both package names and subroutine names may need
205 to be mapped to file and directory names, the Unicode capability of
206 the filesystem becomes important-- and there unfortunately aren't
211 L<perluniintro>, L<encoding>, L<perlrun>, L<bytes>, L<perlunicode>