$a isn't marked as utf-8 because perl has no need to encode it in utf-8.

Also some of the comments in your tests look suspect: 

is( $a, $b, '$a eq $b after utf8 upgrade of $a' );

[download]
But $a isn't upgraded anywhere. 

ok(   Encode::is_utf8($b), '$x is utf-8' );

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You're testing $b, not $x. 

Encode::_utf8_off( $b );
# ...
is( $a, $b, '$a and $b are byte same' );

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_utf8_off does not alter the encoding, it just switches the utf-8 flag, so $a and $b should not be the same, since $a is latin-1 and $b is the same character in utf-8 but marked as latin-1.

That last test is the only one that fails on my machine with perl 5.8.8, and as far as I can see, it's the only one that *should* fail.

A correct way to ensure a string really is utf-8 encoded (assuming it's already flagged correctly as either utf-8 or latin) is to use utf8::upgrade()

See also A UTF8 round trip with MySQL - but read the whole thread!

"What should it profit a man, if he should win a flame war, yet lose his cool?"

In reply to Re: Why does perl not mark variable as utf-8? by Joost
in thread Why does perl not mark variable as utf-8? by Anonymous Monk

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