Perl 5 version 18.3 documentation
bytes - Perl pragma to force byte semantics rather than character semantics
This pragma reflects early attempts to incorporate Unicode into perl and has since been superseded. It breaks encapsulation (i.e. it exposes the innards of how the perl executable currently happens to store a string), and 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.
Perl normally assumes character semantics in the presence of character
data (i.e. data that has come from a source that has been marked as
being of a particular character encoding). When
effect, the encoding is temporarily ignored, and each string is treated
as a series of bytes.
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,
. However, in the scope of the
pragma, $x is treated as a series of bytes - the bytes that make
up the UTF8 encoding - and
chr(), ord(), substr(), index() and rindex() behave similarly.
bytes::substr() does not work as an lvalue().