use Encode;

my $s=chr(0x0160);
printf "chr=<%s> utf8-flag=%s length=%d\n"
  , $s, Encode::is_utf8($s)?'yes':'no', length($s);
#outputs: chr=<?> utf8-flag=yes length=1

Encode::_utf8_off($s);
printf "chr=<%s> utf8-flag=%s length=%d\n"
  , $s, Encode::is_utf8($s)?'yes':'no', length($s);
#outputs: chr=<?> utf8-flag=no length=2