Question about Perl5 extended UTF-8 design

[Otto Stolz]

Am 05.11.2015 um 23:11 schrieb Ilya Zakharevich:
> First of all, “reserved” means that they have no meaning.  Right?

Almost.

“Reserved” means that they have currently no meaning
but may be assigned a meaning, later; hence you ought
not use them lest your programs, or data, be invalidated
by later amendmends of the pertinent specification.

In contrast, “invalid”, or “ill-formed” (Unicode term),
means that the particular bit pattern may never be used
in a sequence that purports to represent Unicode characters.
In practice, that means that no programm is allowed to
send those ill-formed patterns in Unicode-based data exchange,
and every program should refuse to accept those ill-formed
patterns, in Unicode-based data exchange.

What a program does internally is at the discretion (or should
I say: “whim”?) of its author, of course – as long as the
overall effect of the program complies with the standard.

Best wishes,
   Otto Stolz