use strict;
use warnings;
use feature qw( say );

use Tk;
use Data::Dumper;
use Encode;
use Encode qw(is_utf8);

my $mw;             # main window
$mw = MainWindow->new();
$mw->bind( '<Visibility>' => sub {openfile()} );
MainLoop();
exit;

sub openfile{
    my $initfile = $mw->getOpenFile;
    return unless $initfile;
say "initfile $initfile";
say 'Dumper: ', Dumper($initfile);
my $isutf8 = is_utf8($initfile);
say "utf8 flag of initfile is ", $isutf8 ? 'on' : 'off';
if ($isutf8) {
  say '  contains well-formed UTF-8: ', is_utf8($initfile, 1) ? 'ja' : 'nein';
}

    $initfile = encode('iso-8859-1', $initfile, Encode::FB_CROAK);
say "initfile $initfile";
say 'Dumper: ', Dumper($initfile);
$isutf8 = is_utf8($initfile);
say "utf8 flag of initfile is ", $isutf8 ? 'on' : 'off';
if ($isutf8) {
  say '  contains well-formed UTF-8: ', is_utf8($initfile, 1) ? 'ja' : 'nein';
}

    open( my $SUDO, '<', $initfile ) or die("can't open $initfile: $!");
say "opened $initfile";
my @game = <$SUDO>;
say "game\n", @game;
close($SUDO);
    return;
}

initfile U:/Benutzer/Klaus/Perl/Sudoku-Trainer/Rätsel/Aufg/Aufg54a.txt
Dumper: $VAR1 = "U:/Benutzer/Klaus/Perl/Sudoku-Trainer/R\x{e4}tsel/Aufg/Aufg54a.txt";

utf8 flag of initfile is on
  contains well-formed UTF-8: ja
initfile U:/Benutzer/Klaus/Perl/Sudoku-Trainer/Rätsel/Aufg/Aufg54a.txt
Dumper: $VAR1 = 'U:/Benutzer/Klaus/Perl/Sudoku-Trainer/Rätsel/Aufg/Aufg54a.txt';

utf8 flag of initfile is off
opened U:/Benutzer/Klaus/Perl/Sudoku-Trainer/Rätsel/Aufg/Aufg54a.txt
game
-2- --- ---
4-- --- 836
--- -5- --7

7-5 --- ---
--2 --- -4-
8-- -9- 2-1

--3 7-2 ---
--1 -69 ---
--- 3-- 4-9

initfile U:/Benutzer/Klaus/Perl/Sudoku-Trainer/Rätsel/Aufg/Aufg54a.txt
Dumper: $VAR1 = "U:/Benutzer/Klaus/Perl/Sudoku-Trainer/R\x{e4}tsel/Aufg/Aufg54a.txt";

utf8 flag of initfile is on
  contains well-formed UTF-8: ja
eval_err: can't open U:/Benutzer/Klaus/Perl/Sudoku-Trainer/Rätsel
/Aufg/Aufg54a.txt: No such file or directory at U:/Benutzer/Klaus
/Perl/Sudoku-Trainer/Devel/Trainer/GUI.pm line 395.