-corresponding character sequence. The UTF-8 flag is turned on only if
-the source string contains multiple-byte I<UTF-X> characters. If
-I<$string> is invalid as I<UTF-X>, returns false; otherwise returns
-true.
+corresponding character sequence. That is, it replaces each sequence of
+characters in the string whose ords represent a valid UTF-X byte
+sequence, with the corresponding single character. The UTF-8 flag is
+turned on only if the source string contains multiple-byte I<UTF-X>
+characters. If I<$string> is invalid as I<UTF-X>, returns false;
+otherwise returns true.
+
+ my $a = "\xc4\x80"; # $a contains two characters, with ords 0xc4 and 0x80
+ utf8::decode($a); # $a contains one character, with ord 0x100