open(my $fh_in, '<:encoding(iso-8859-1)', $qfn_in)
    or die("Can't open \"$qfn_in\": $!\n");

open(my $fh_out, '>:encoding(UTF-8)', $qfn_out)
    or die("Can't create \"$qfn_out\": $!\n");

print $fh_out $_ while <$fh_in>;