utf8::downgrade( my $d = "\xE3" );
printf "%vX\n", $d;                          # E3
printf "%d\n", utf8::is_utf8( $d ) ? 1 : 0;  # 0
printf "%vX\n", transform( $d );             # E3

utf8::upgrade(  my $u = "\xE3" );
printf "%vX\n", $u;                          # E3
printf "%d\n", utf8::is_utf8( $u ) ? 1 : 0;  # 1
printf "%vX\n", transform( $u );             # C3.A3

utf8::upgrade( my $w = "\x{2660}" );
printf "%vX\n", $w;                          # 2660
printf "%d\n", utf8::is_utf8( $w ) ? 1 : 0;  # 1
printf "%vX\n", transform( $w );             # E2.99.A0