The C<use utf8> pragma tells the Perl parser to allow UTF-8 in the
program text in the current lexical scope (allow UTF-EBCDIC on EBCDIC based
-platforms). The C<no utf8> pragma tells Perl to switch back to treating
+platforms). The C<no utf8> pragma tells Perl to switch back to treating
the source text as literal bytes in the current lexical scope.
This pragma is primarily a compatibility device. Perl versions
Converts internal representation of string to the Perl's internal
I<UTF-X> form. Returns the number of octets necessary to represent
-the string as I<UTF-X>.
+the string as I<UTF-X>. Note that this should not be used to convert
+a legacy byte encoding to Unicode: use Encode for that. Affected
+by the encoding pragma.
=item * utf8::downgrade($string[, CHECK])
Converts internal representation of string to be un-encoded bytes.
+Note that this should not be used to convert Unicode back to a legacy
+byte encoding: use Encode for that. B<Not> affected by the encoding
+pragma.
=item * utf8::encode($string)
-Converts (in-place) I<$string> from logical characters to octet sequence
-representing it in Perl's I<UTF-X> encoding.
+Converts (in-place) I<$string> from logical characters to octet
+sequence representing it in Perl's I<UTF-X> encoding. Note that this
+should not be used to convert a legacy byte encoding to Unicode: use
+Encode for that.
=item * $flag = utf8::decode($string)
Attempts to convert I<$string> in-place from Perl's I<UTF-X> encoding
-into logical characters.
+into logical characters. Note that this should not be used to convert
+Unicode back to a legacy byte encoding: use Encode for that.
+
+=item * $flag = utf8::valid(STRING)
+
+[INTERNAL] Test whether STRING is in a consistent state. Will return
+true if string is held as bytes, or is well-formed UTF-8 and has the
+UTF-8 flag on. Main reason for this routine is to allow Perl's
+testsuite to check that operations have left strings in a consistent
+state.
=back
+C<utf8::encode> is like C<utf8::upgrade>, but the UTF8 flag is cleared.
+See L<perlunicode> for more on the UTF8 flag and the C API functions
+C<sv_utf8_upgrade>, C<sv_utf8_downgrade>, C<sv_utf8_encode>,
+and C<sv_utf8_decode>, which are wrapped by the Perl functions
+C<utf8::upgrade>, C<utf8::downgrade>, C<utf8::encode> and
+C<utf8::decode>.
+
=head1 SEE ALSO
L<perlunicode>, L<bytes>