losing utf8 flag on strings?

Can anyone explain what I'm doing wrong?
I have this recurring problem of strings not being flagged
as utf8, when -- I believe -- they should be.

One of those cases is in decode_entities() from the module
HTML::Entities, but I have other occurances too (e.g. in Plucene).

When I run this program:

########### cut here
#!/usr/bin/perl
use HTML::Entities;
use Encode;
print "This is perl ", $], "\n";

$s = "€";
$t = decode_entities($s);
$u = decode("utf8", $t, Decode::FB_CROAK);

print "t: ", Encode::is_utf8($t) ? "is" : "not", " utf8", "\n";
print "u: ", Encode::is_utf8($u) ? "is" : "not", " utf8", "\n";
print "t: ", ($t eq "\x{20ac}") ? "is" : "not", " Eurosign\n";
print "u: ", ($u eq "\x{20ac}") ? "is" : "not", " Eurosign\n";
########### cut here

I get this output:

This is perl 5.008005
t: not utf8
u: is utf8
t: not Eurosign
u: is Eurosign

I would expect that $t does have the utf8 flag set,
as indicated in the manpage of HTML::Entities :

        decode_entities( $string )
            This routine replaces HTML entities found in the
            $string with the corresponding ISO-8859-1 character,
            and if possible (under perl 5.8 or later) will replace
            to Unicode characters.  Unrecognized entities are left
            alone.

Why do I have to force the utf8 flag using decode("utf8",..) ?

One of my guesses is that the problem lies in XS-processing of strings
where the utf8 flag is not set correctly.  True?
Why does nobody else complain then?

Is my setup wrong?  (Tried this on different installations including
a brand new Fedore Core 3...)


-- 
Paul Bijnens, Xplanation                            Tel  +32 16 397.511
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