/[\xC0-\xFF][\x80-\xBF]+/

##</code><code>##

my($utf8, $bare) = (0, 0);
use bytes;
while(/(?=[\x80-\xFF])(?:[\xC0-\xFF][\x80-\xBF]+|(.))/g) {
    $bare++ if defined $1;
    $utf8++ unless defined $1;
}
print <<"END"
utf-8: $utf8
bare: $bare
END