use bytes (Programming Perl)

31.5. use bytes

use bytes;
no bytes;

The use bytes pragma disables character semantics for the rest of the lexical scope in which it appears. The no bytes pragma 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 (that is, data from a source marked as being of a particular character encoding).

To understand the implications and differences between character semantics and byte semantics, see Chapter 15, "Unicode". A visit to Tokyo might also help.