clearing the utf8 flag

I have a program that reads and writes (among others) strings that
should be utf8 encoded.  I say "should", because somewhere deep
inside the dark corners of that program, sometimes, the utf8 flag on
a string is lost. (I'm still investigating where, tips to attack
such a problem are welcome.)

When writing the string, the program clears the utf8 flag
and writes a simple string of octets using:

     $s = encode("utf8", $s) if $s =~ /[^\x00-\x7f]/;
     $n = length($s);   # yes, we need length in bytes
     ...
     print $s;

Why would someone test for pure 7-bit strings instead of:

     $s = encode("utf8", $s) if Encode::is_utf8($s);

which seems superior to avoid double utf8 encodings,
should the utf8-flag be lost.  And it's faster.

Or even simply:     Encode::_utf8_off($s)

The problem is that I'm usually wrong.  Am I this time?
Am I missing something?  Or do I need more coffee?


-- 
Paul Bijnens, Xplanation                            Tel  +32 16 397.511
Technologielaan 21 bus 2, B-3001 Leuven, BELGIUM    Fax  +32 16 397.512
http://www.xplanation.com/          email:  [email protected]
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