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This pragma reflects early attempts to incorporate Unicode into perl and has since been superseded.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.
The use bytes
pragma disables character semantics for the rest of the
lexical scope in which it appears. no bytes
can be used to reverse
the effect of use bytes
within the current lexical scope.
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 use bytes
is in
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,
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
:
chr(), ord(), substr(), index() and rindex() behave similarly.
For more on the implications and differences between character semantics and byte semantics, see perluniintro and perlunicode.
bytes::substr() does not work as an lvalue().