use Devel::Peek qw( Dump );

my $s = chr(0xE9);

say length($s);              # 1
say $s eq "\xE9" ?1:0;       # 1
say utf8::is_utf8($s) ?1:0;  # 0
Dump($s);                    # PV contains E9

utf8::upgrade($s);

say length($s);              # 1 The string hasn't changed
say $s eq "\xE9" ?1:0;       # 1 
say utf8::is_utf8($s) ?1:0;  # 1 But it's now stored differently.
Dump($s);                    # PV contains C3 A9

utf8::downgrade($s);

say length($s);              # 1
say $s eq "\xE9" ?1:0;       # 1
say utf8::is_utf8($s) ?1:0;  # 0
Dump($s);                    # PV contains E9