utf8(3)

NAME

       utf8 - Perl pragma to enable/disable UTF-8 (or UTF-EBCDIC) in source
       code

SYNOPSIS

           use utf8;
           no utf8;

DESCRIPTION

       The "use utf8" pragma tells the Perl parser to allow UTF-8 in the pro-
       gram text in the current lexical scope (allow UTF-EBCDIC on EBCDIC
       based platforms).  The "no utf8" pragma tells Perl to switch back to
       treating the source text as literal bytes in the current lexical scope.

       This pragma is primarily a compatibility device.  Perl versions earlier
       than 5.6 allowed arbitrary bytes in source code, whereas in future we
       would like to standardize on the UTF-8 encoding for source text.  Until
       UTF-8 becomes the default format for source text, this pragma should be
       used to recognize UTF-8 in the source.  When UTF-8 becomes the standard
       source format, this pragma will effectively become a no-op.  For conve-
       nience in what follows the term UTF-X is used to refer to UTF-8 on
       ASCII and ISO Latin based platforms and UTF-EBCDIC on EBCDIC based
       platforms.

       Enabling the "utf8" pragma has the following effect:

       o   Bytes in the source text that have their high-bit set will be
           treated as being part of a literal UTF-8 character.  This includes
           most literals such as identifier names, string constants, and con-
           stant regular expression patterns.

           On EBCDIC platforms characters in the Latin 1 character set are
           treated as being part of a literal UTF-EBCDIC character.

       Note that if you have bytes with the eighth bit on in your script (for
       example embedded Latin-1 in your string literals), "use utf8" will be
       unhappy since the bytes are most probably not well-formed UTF-8.  If
       you want to have such bytes and use utf8, you can disable utf8 until
       the end the block (or file, if at top level) by "no utf8;".

       Utility functions

       The following functions are defined in the "utf8::" package by the perl
       core.

       o $num_octets = utf8::upgrade($string);
           Converts (in-place) internal representation of string to Perl's
           internal UTF-X form.  Returns the number of octets necessary to
           represent the string as UTF-X.  Can be used to make sure that the
           UTF-8 flag is on, so that "\w" or "lc()" work as expected on
           strings containing characters in the range 0x80-0xFF.  Note that
           this should not be used to convert a legacy byte encoding to Uni-
           code: use Encode for that.  Affected by the encoding pragma.

       o utf8::downgrade($string[, FAIL_OK])
           Converts (in-place) internal representation of string to be un-
           encoded bytes.  Returns true on success. On failure dies or, if the
           value of FAIL_OK is true, returns false.  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.  Note that this should not be used to convert Uni-
           code back to a legacy byte encoding: use Encode for that.  Not
           affected by the encoding pragma.

       o utf8::encode($string)
           Converts (in-place) $string from logical characters to octet
           sequence representing it in Perl's UTF-X encoding. Same as
           Encode::encode_utf8(). Note that this should not be used to convert
           a legacy byte encoding to Unicode: use Encode for that.

       o $flag = utf8::decode($string)
           Attempts to convert $string in-place from Perl's UTF-X encoding
           into logical characters. Same as Encode::decode_utf8(). Note that
           this should not be used to convert Unicode back to a legacy byte
           encoding: use Encode for that.

       o $flag = utf8::valid(STRING)
           [INTERNAL] Test whether STRING is in a consistent state.  Will
           return true if string is held as bytes, or is well-formed UTF-8 and
           has the UTF-8 flag on.  Main reason for this routine is to allow
           Perl's testsuite 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 for more on the UTF8 flag and the C API functions
       "sv_utf8_upgrade", "sv_utf8_downgrade", "sv_utf8_encode", and
       "sv_utf8_decode", which are wrapped by the Perl functions
       "utf8::upgrade", "utf8::downgrade", "utf8::encode" and "utf8::decode".
       Note that in the Perl 5.8.0 implementation the functions utf8::valid,
       utf8::encode, utf8::decode, utf8::upgrade, and utf8::downgrade are
       always available, without a "require utf8" statement-- this may change
       in future releases.

BUGS

       One can have Unicode in identifier names, but not in package/class or
       subroutine names.  While some limited functionality towards this does
       exist as of Perl 5.8.0, that is more accidental than designed; use of
       Unicode for the said purposes is unsupported.

       One reason of this unfinishedness is its (currently) inherent unporta-
       bility: since both package names and subroutine names may need to be
       mapped to file and directory names, the Unicode capability of the
       filesystem becomes important-- and there unfortunately aren't portable
       answers.

utf8(3)

NAME

SYNOPSIS

DESCRIPTION

BUGS

SEE ALSO