use utf8 affects string literals in the source (and STDIN and STDOUT?). Strings stored in a data file won't be affected by it.

Simply specify the encoding of the data file when opening the data file.

open(my $fh, '<:encoding(UTF-8)', $language_qfn) or die;
while (<$fh>) {
   ...
}
[download]

If the you have a handle and not a file name, use binmode.

binmode(STDIN, ':encoding(UTF-8)');
while (<STDIN>) {
   ...
}
[download]

Or decode the string explicitly

use Encode qw( decode );

open(my $fh, '<', $language_qfn) or die;
while (<$fh>) {
   $_ = decode('UTF-8', $_);
   ...
}
[download]

Output is very similar. Set the encoding on the output handle or use encode.

open(my $fh, '>:encoding(UTF-8)', $output_fqn) or die;
print $fh ($text);
[download]

binmode(STDOUT, ':encoding(UTF-8)');
print($text);
[download]

use Encode qw( encode );
open(my $fh, '>', $output_fqn) or die;
print $fh (encode('UTF-8', $text));
[download]

Update: Added output info.