require bytes;

$x = "\xC9\xCA\xCB\xCC";

utf8::downgrade($x);
print(substr($x,1,1)        eq "\xCA" ?1:0,"\n");  # 1
utf8::upgrade($x);
print(substr($x,1,1)        eq "\xCA" ?1:0,"\n");  # 1

utf8::downgrade($x);
print(bytes::substr($x,1,1) eq "\xCA" ?1:0,"\n");  # 1
utf8::upgrade($x);
print(bytes::substr($x,1,1) eq "\xCA" ?1:0,"\n");  # 0