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<big>&nbsp;utf8 - Perl pragma to enable/disable UTF-8 in source code</big>
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<ul>

<li><a href="#name">NAME</a></li>
	<li><a href="#synopsis">SYNOPSIS</a></li>
	<li><a href="#description">DESCRIPTION</a></li>
	<ul>

<li><a href="#utility_functions">Utility functions</a></li>
	</ul>

<h1><a name="name">NAME</a></h1>
utf8 - Perl pragma to enable/disable UTF-8 (or UTF-EBCDIC) in source code


<hr />
<h1><a name="synopsis">SYNOPSIS</a></h1>
<pre>
 use utf8;
 no utf8;</pre>
<pre>
 # Convert a Perl scalar to/from UTF-8.
 $num_octets = utf8::upgrade($string);
 $success = utf8::downgrade($string[, FAIL_OK]);</pre>
<pre>
 # Change the native bytes of a Perl scalar to/from UTF-8 bytes.
 utf8::encode($string);
 utf8::decode($string);</pre>
<pre>
 $flag = utf8::is_utf8(STRING); # since Perl 5.8.1
 $flag = utf8::valid(STRING);</pre>


<hr />
<h1><a name="description">DESCRIPTION</a></h1>
The <code>use utf8</code> pragma tells the Perl parser to allow UTF-8 in the
program text in the current lexical scope (allow UTF-EBCDIC on EBCDIC based
platforms). The <code>no utf8</code> pragma tells Perl to switch back to treating
the source text as literal bytes in the current lexical scope.
Do not use this pragma for anything else than telling Perl that your
script is written in UTF-8. The utility functions described below are
directly usable without <code>use utf8;</code>.
Because it is not possible to reliably tell UTF-8 from native 8 bit
encodings, you need either a Byte Order Mark at the beginning of your
source code, or <code>use utf8;</code>, to instruct perl.
When UTF-8 becomes the standard source format, this pragma will
effectively become a no-op. For convenience 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.
See also the effects of the <code>-C</code> switch and its cousin, the
<code>$ENV{PERL_UNICODE}</code>, in <a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/pod/perlrun.html">the perlrun manpage</a>.
Enabling the <a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/pod/perlrun.html#utf8"><code>utf8</code></a> pragma has the following effect:
<ul>
<li>
Bytes in the source text that have their high-bit set will be treated
as being part of a literal UTF-X sequence. This includes most
literals such as identifier names, string constants, and constant
regular expression patterns.
On EBCDIC platforms characters in the Latin 1 character set are
treated as being part of a literal UTF-EBCDIC character.
</li>
</ul>
Note that if you have bytes with the eighth bit on in your script
(for example embedded Latin-1 in your string literals), <code>use utf8</code>
will be unhappy since the bytes are most probably not well-formed
UTF-X. If you want to have such bytes under <code>use utf8</code>, you can disable
this pragma until the end the block (or file, if at top level) by
<code>no utf8;</code>.


<h2><a name="utility_functions">Utility functions</a></h2>
The following functions are defined in the <a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/pod/perlrun.html#utf8"><code>utf8::</code></a> package by the
Perl core. You do not need to say <code>use utf8</code> to use these and in fact
you should not say that unless you really want to have UTF-8 source code.
<ul>
<li><a name="upgrade" class="item">$num_octets = utf8::upgrade($string)</a>

Converts in-place the internal octet sequence in the native encoding
(Latin-1 or EBCDIC) to the equivalent character sequence in UTF-X.
$string already encoded as characters does no harm. Returns the
number of octets necessary to represent the string as UTF-X. Can be
used to make sure that the UTF-8 flag is on, so that <a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/pod/perlrun.html#w"><code>\w</code></a> or <a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/pod/perlfunc.html#lc"><code>lc()</code></a>
work as Unicode on strings containing characters in the range 0x80-0xFF
(on ASCII and derivatives).
Note that this function does not handle arbitrary encodings.
Therefore Encode is recommended for the general purposes; see also
<a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/lib/Encode.html">the Encode manpage</a>.
</li>
<li><a name="downgrade" class="item">$success = utf8::downgrade($string[, FAIL_OK])</a>

Converts in-place the internal octet sequence in UTF-X to the
equivalent octet sequence in the native encoding (Latin-1 or EBCDIC).
$string already encoded as native 8 bit does no harm. Can be used to
make sure that the UTF-8 flag is off, e.g. when you want to make sure
that the <a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/pod/perlvar.html#substr"><code>substr()</code></a> or <a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/pod/perlfunc.html#length"><code>length()</code></a> function works with the usually faster
byte algorithm.
Fails if the original UTF-X sequence cannot be represented in the
native 8 bit encoding. On failure dies or, if the value of <code>FAIL_OK</code> is
true, returns false.
Returns true on success.
Note that this function does not handle arbitrary encodings.
Therefore Encode is recommended for the general purposes; see also
<a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/lib/Encode.html">the Encode manpage</a>.
</li>
<li><a name="encode" class="item">utf8::encode($string)</a>

Converts in-place the character sequence to the corresponding octet
sequence in UTF-X. The UTF8 flag is turned off, so that after this
operation, the string is a byte string. Returns nothing.
Note that this function does not handle arbitrary encodings.
Therefore Encode is recommended for the general purposes; see also
<a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/lib/Encode.html">the Encode manpage</a>.
</li>
<li><a name="decode" class="item">$success = utf8::decode($string)</a>

Attempts to convert in-place the octet sequence in UTF-X to the
corresponding character sequence. The UTF-8 flag is turned on only if
the source string contains multiple-byte UTF-X characters. If
$string is invalid as UTF-X, returns false; otherwise returns
true.
Note that this function does not handle arbitrary encodings.
Therefore Encode is recommended for the general purposes; see also
<a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/lib/Encode.html">the Encode manpage</a>.
</li>
<li><a name="is_utf8" class="item">$flag = utf8::is_utf8(STRING)</a>

(Since Perl 5.8.1) Test whether STRING is in UTF-8 internally.
Functionally the same as Encode::is_utf8().
</li>
<li><a name="valid" class="item">$flag = utf8::valid(STRING)</a>

[INTERNAL] Test whether STRING is in a consistent state regarding
UTF-8. Will return true is well-formed UTF-8 and has the UTF-8 flag
on or if string is held as bytes (both these states are 'consistent').
Main reason for this routine is to allow Perl's testsuite to check
that operations have left strings in a consistent state. You most
probably want to use utf8::is_utf8() instead.
</li>
</ul>
<code>utf8::encode</code> is like <code>utf8::upgrade</code>, but the UTF8 flag is
cleared. See <a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/pod/perlunicode.html">the perlunicode manpage</a> for more on the UTF8 flag and the C API
functions <code>sv_utf8_upgrade</code>, <code>sv_utf8_downgrade</code>, <code>sv_utf8_encode</code>,
and <code>sv_utf8_decode</code>, which are wrapped by the Perl functions
<code>utf8::upgrade</code>, <code>utf8::downgrade</code>, <code>utf8::encode</code> and
<code>utf8::decode</code>. Also, the functions utf8::is_utf8, utf8::valid,
utf8::encode, utf8::decode, utf8::upgrade, and utf8::downgrade are
actually internal, and thus always available, without a <code>require utf8</code>
statement.


<hr />
<h1><a name="bugs">BUGS</a></h1>
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
unportability: 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.


<hr />
<h1><a name="see_also">SEE ALSO</a></h1>
<a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/pod/perlunitut.html">the perlunitut manpage</a>, <a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/pod/perluniintro.html">the perluniintro manpage</a>, <a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/pod/perlrun.html">the perlrun manpage</a>, <a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/lib/bytes.html">the bytes manpage</a>, <a href="file://C|\ADE\aime_smenon_perl_090715\perl\html/pod/perlunicode.html">the perlunicode manpage</a>
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<big>&nbsp;utf8 - Perl pragma to enable/disable UTF-8 in source code</big>
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