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