=item * $flag = utf8::valid(STRING)
[INTERNAL] Test whether STRING is in a consistent state regarding
UTF-8. Will return true if it is well-formed UTF-8 and has the UTF-8 flag
on B<or> if STRING is held as bytes (both these states are 'consistent').
=item * $flag = utf8::valid(STRING)
[INTERNAL] Test whether STRING is in a consistent state regarding
UTF-8. Will return true if it is well-formed UTF-8 and has the UTF-8 flag
on B<or> if STRING is held as bytes (both these states are 'consistent').