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 $num_octets = utf8::upgrade($string);
35 $success = utf8::downgrade($string[, FAIL_OK]);
37 utf8::encode($string);
38 utf8::decode($string);
40 $flag = utf8::is_utf8(STRING); # since Perl 5.8.1
41 $flag = utf8::valid(STRING);
45 The C<use utf8> pragma tells the Perl parser to allow UTF-8 in the
46 program text in the current lexical scope (allow UTF-EBCDIC on EBCDIC based
47 platforms). The C<no utf8> pragma tells Perl to switch back to treating
48 the source text as literal bytes in the current lexical scope.
50 This pragma is primarily a compatibility device. Perl versions
51 earlier than 5.6 allowed arbitrary bytes in source code, whereas
52 in future we would like to standardize on the UTF-8 encoding for
55 Until UTF-8 becomes the default format for source text, either this
56 pragma or the L</encoding> pragma should be used to recognize UTF-8
57 in the source. When UTF-8 becomes the standard source format, this
58 pragma will effectively become a no-op. For convenience in what
59 follows the term I<UTF-X> is used to refer to UTF-8 on ASCII and ISO
60 Latin based platforms and UTF-EBCDIC on EBCDIC based platforms.
62 Enabling the C<utf8> pragma has the following effect:
68 Bytes in the source text that have their high-bit set will be treated
69 as being part of a literal UTF-8 character. This includes most
70 literals such as identifier names, string constants, and constant
71 regular expression patterns.
73 On EBCDIC platforms characters in the Latin 1 character set are
74 treated as being part of a literal UTF-EBCDIC character.
78 Note that if you have bytes with the eighth bit on in your script
79 (for example embedded Latin-1 in your string literals), C<use utf8>
80 will be unhappy since the bytes are most probably not well-formed
81 UTF-8. If you want to have such bytes and use utf8, you can disable
82 utf8 until the end the block (or file, if at top level) by C<no utf8;>.
84 If you want to automatically upgrade your 8-bit legacy bytes to UTF-8,
85 use the L</encoding> pragma instead of this pragma. For example, if
86 you want to implicitly upgrade your ISO 8859-1 (Latin-1) bytes to UTF-8
87 as used in e.g. C<chr()> and C<\x{...}>, try this:
89 use encoding "latin-1";
93 In case you are wondering: yes, C<use encoding 'utf8';> works much
94 the same as C<use utf8;>.
96 =head2 Utility functions
98 The following functions are defined in the C<utf8::> package by the
99 Perl core. You do not need to say C<use utf8> to use these and in fact
100 you should not unless you really want to have UTF-8 source code.
104 =item * $num_octets = utf8::upgrade($string)
106 Converts (in-place) internal representation of string to Perl's
107 internal I<UTF-X> form. Returns the number of octets necessary to
108 represent the string as I<UTF-X>. Can be used to make sure that the
109 UTF-8 flag is on, so that C<\w> or C<lc()> work as expected on strings
110 containing characters in the range 0x80-0xFF (oon ASCII and
111 derivatives). Note that this should not be used to convert a legacy
112 byte encoding to Unicode: use Encode for that. Affected by the
115 =item * $success = utf8::downgrade($string[, FAIL_OK])
117 Converts (in-place) internal representation of string to be un-encoded
118 bytes. Returns true on success. On failure dies or, if the value of
119 FAIL_OK is true, returns false. Can be used to make sure that the
120 UTF-8 flag is off, e.g. when you want to make sure that the substr()
121 or length() function works with the usually faster byte algorithm.
122 Note that this should not be used to convert Unicode back to a legacy
123 byte encoding: use Encode for that. B<Not> affected by the encoding
126 =item * utf8::encode($string)
128 Converts (in-place) I<$string> from logical characters to octet
129 sequence representing it in Perl's I<UTF-X> encoding. Returns
130 nothing. Same as Encode::encode_utf8(). Note that this should not be
131 used to convert a legacy byte encoding to Unicode: use Encode for
134 =item * utf8::decode($string)
136 Attempts to convert I<$string> in-place from Perl's I<UTF-X> encoding
137 into logical characters. Returns nothing. Same as Encode::decode_utf8().
138 Note that this should not be used to convert Unicode back to a legacy
139 byte encoding: use Encode for that.
141 =item * $flag = utf8::is_utf8(STRING)
143 (Since Perl 5.8.1) Test whether STRING is in UTF-8. Functionally
144 the same as Encode::is_utf8().
146 =item * $flag = utf8::valid(STRING)
148 [INTERNAL] Test whether STRING is in a consistent state regarding
149 UTF-8. Will return true is well-formed UTF-8 and has the UTF-8 flag
150 on B<or> if string is held as bytes (both these states are 'consistent').
151 Main reason for this routine is to allow Perl's testsuite to check
152 that operations have left strings in a consistent state. You most
153 probably want to use utf8::is_utf8() instead.
157 C<utf8::encode> is like C<utf8::upgrade>, but the UTF8 flag is
158 cleared. See L<perlunicode> for more on the UTF8 flag and the C API
159 functions C<sv_utf8_upgrade>, C<sv_utf8_downgrade>, C<sv_utf8_encode>,
160 and C<sv_utf8_decode>, which are wrapped by the Perl functions
161 C<utf8::upgrade>, C<utf8::downgrade>, C<utf8::encode> and
162 C<utf8::decode>. Note that in the Perl 5.8.0 and 5.8.1 implementation
163 the functions utf8::is_utf8, utf8::valid, utf8::encode, utf8::decode,
164 utf8::upgrade, and utf8::downgrade are always available, without a
165 C<require utf8> statement-- this may change in future releases.
169 One can have Unicode in identifier names, but not in package/class or
170 subroutine names. While some limited functionality towards this does
171 exist as of Perl 5.8.0, that is more accidental than designed; use of
172 Unicode for the said purposes is unsupported.
174 One reason of this unfinishedness is its (currently) inherent
175 unportability: since both package names and subroutine names may need
176 to be mapped to file and directory names, the Unicode capability of
177 the filesystem becomes important-- and there unfortunately aren't
182 L<perluniintro>, L<encoding>, L<perlunicode>, L<bytes>