I can reproduce* your problem in 5.8.8 and 5.10.0. It seems to be a bug in Perl.

I have heard people speak highly of Perl6::Form, a module providing Perl6 format syntax to Perl5. Perhaps that would be a viable alternative.

* — I used the following to populate @ARGV:

use Encode         qw( encode );
use HTML::Entities qw( decode_entities );
@ARGV = encode('UTF-8', decode_entities("l'été sera chau
+d"));
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