The pragma is a per script, not a per block lexical. Only the last
C<use encoding> matters, and it affects B<the whole script>.
+Notice that only literals (string or regular expression) having only
+legacy code points are affected: if you mix data like this
+
+ \xDF\x{100}
+
+the data is assumed to be in (Latin 1 and) Unicode, not in your native
+encoding. In other words, this will match in "greek":
+
+ "\xDF" =~ /\x{3af}/
+
+but this will not
+
+ "\xDF\x{100}" =~ /\x{3af}\x{100}/
+
+since the C<\xDF> on the left will B<not> be upgraded to C<\x{3af}>
+because of the C<\x{100}> on the left. You should not be mixing your
+legacy data and Unicode in the same string.
+
If no encoding is specified, the environment variable L<PERL_ENCODING>
is consulted. If that fails, "latin1" (ISO 8859-1) is assumed. If no
encoding can be found, C<Unknown encoding '...'> error will be thrown.
=head1 KNOWN PROBLEMS
-Literals in regular expressions are not affected by this pragma.
-They very probably should.
+For native multibyte encodings (either fixed or variable length)
+the current implementation of the regular expressions may introduce
+recoding errors for longer regular expression literals than 127 bytes.
=head1 SEE ALSO