Provided by: perl-doc_5.30.0-9build1_all bug


       bytes - Perl pragma to expose the individual bytes of characters


       Because the bytes pragma breaks encapsulation (i.e. it exposes the innards of how the perl
       executable currently happens to store a string), the byte values that result are in an
       unspecified encoding.

       Use of this module for anything other than debugging purposes is strongly discouraged.  If
       you feel that the functions here within might be useful for your application, this
       possibly indicates a mismatch between your mental model of Perl Unicode and the current
       reality. In that case, you may wish to read some of the perl Unicode documentation:
       perluniintro, perlunitut, perlunifaq and perlunicode.


           use bytes;
           ... chr(...);       # or bytes::chr
           ... index(...);     # or bytes::index
           ... length(...);    # or bytes::length
           ... ord(...);       # or bytes::ord
           ... rindex(...);    # or bytes::rindex
           ... substr(...);    # or bytes::substr
           no bytes;


       Perl's characters are stored internally as sequences of one or more bytes.  This pragma
       allows for the examination of the individual bytes that together comprise a character.

       Originally the pragma was designed for the loftier goal of helping incorporate Unicode
       into Perl, but the approach that used it was found to be defective, and the one remaining
       legitimate use is for debugging when you need to non-destructively examine characters'
       individual bytes.  Just insert this pragma temporarily, and remove it after the debugging
       is finished.

       The original usage can be accomplished by explicit (rather than this pragma's implicit)
       encoding using the Encode module:

           use Encode qw/encode/;

           my $utf8_byte_string   = encode "UTF8",   $string;
           my $latin1_byte_string = encode "Latin1", $string;

       Or, if performance is needed and you are only interested in the UTF-8 representation:

           utf8::encode(my $utf8_byte_string = $string);

       "no bytes" can be used to reverse the effect of "use bytes" within the current lexical

       As an example, when Perl sees "$x = chr(400)", it encodes the character in UTF-8 and
       stores it in $x. Then it is marked as character data, so, for instance, "length $x"
       returns 1. However, in the scope of the "bytes" pragma, $x is treated as a series of bytes
       - the bytes that make up the UTF8 encoding - and "length $x" returns 2:

        $x = chr(400);
        print "Length is ", length $x, "\n";     # "Length is 1"
        printf "Contents are %vd\n", $x;         # "Contents are 400"
            use bytes; # or "require bytes; bytes::length()"
            print "Length is ", length $x, "\n"; # "Length is 2"
            printf "Contents are %vd\n", $x;     # "Contents are 198.144 (on
                                                 # ASCII platforms)"

       "chr()", "ord()", "substr()", "index()" and "rindex()" behave similarly.

       For more on the implications, see perluniintro and perlunicode.

       "bytes::length()" is admittedly handy if you need to know the byte length of a Perl
       scalar.  But a more modern way is:

          use Encode 'encode';
          length(encode('UTF-8', $scalar))


       "bytes::substr()" does not work as an lvalue().


       perluniintro, perlunicode, utf8, Encode