use charnames ':full';

{
    my %escapes = (
        '&' => '&',
        '<' => '&lt;',   '>' => '&gt;',
        '"' => '&quot;', "'" => '&apos;',
    );

    sub xml_text
        { (my $s = $_[0]) =~ s/([<&])/$escapes{$1}/g;  $s       }
    sub xml_att_val
        { (my $s = $_[0]) =~ s/([<&"])/$escapes{$1}/g; qq{"$s"} }
}

my $s_7bit  = "A";
my $s_8bit  = "\N{LATIN CAPITAL LETTER A WITH CIRCUMFLEX}";
my $s_32bit = "\N{BLACK SPADE SUIT}";

##</code><code>##

open(my $fh, '>:encoding(UTF-8)', $qfn)
    or die;

print($fh qq{<?xml version="1.0" encoding="UTF-8"?>\n});
print($fh qq{<foo>\n});
print($fh qq{  <bar>}, xml_text($s_7bit), qq{</bar>\n});
print($fh qq{  <bar>}, xml_text($s_8bit), qq{</bar>\n});
print($fh qq{  <bar>}, xml_text($s_32bit), qq{</bar>\n});
print($fh qq{</foo>\n});