open my $fh, '<:encoding(UTF-8)', $filename
        or die "Couldn't open '$filename': $!";

##</code><code>##

    open my $fh, '>:encoding(UTF-8)', $filename
        or die "Couldn't open '$filename': $!";

##</code><code>##

use charnames ':full';
use Encode 'encode';

open my $fh, '>', $filename
    or die "Couldn't create '$filename': $!";

my $output = "MOT\N{CAPITAL LETTER O WITH DIAERESIS}RHEAD";
my $output_bytes = encode( 'UTF-8', $output );
print $fh $output_bytes;