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. A visit to Tokyo might also help.