$ perl -le'use open ":std", ":locale"; $_="\xE0 la plage"; utf8::downgrade($_); print "\u$_"'
à la plage

$ perl -le'use open ":std", ":locale"; $_="\xE0 la plage"; utf8::upgrade($_); print "\u$_"'
À la plage

##</code><code>##

open(my $fh, '<:encoding(UTF-8)', $qfn)
    or die("Can't open file $qfn: $!\n");