use FindBin;
....

my $image;
my $mw = MainWindow->new();

our @files = glob("$FindBin::Bin/test/*.jpg");

my ($imageFile) = &GetNextFile();

my $button = $imageFrame->Button(-image => $image)
    ->pack(-fill => 'both', -expand => 1);

$button->configure(-command => sub {
    ($imageFile) = &GetNextFile();
    $button->configure(-image => $image);
});

&Tk::MainLoop;
# ---------------------------------------
sub GetNextFile {
  while (my $file = shift(@files)) {
    next if -d "$inputDir/$file";

    if ($file =~ /\.jpe?g$/) {
      unless (ref($image)) {
        eval {
          $image = $imageFrame->Photo(-file => "$file", -format => 'jpeg');
        };
        if ($@) {
          print "$file: $@\n"; $image = undef; next;
        } # if
      } # unless

    return (&File::Basename::basename($file));
  } # while
} # GetNextFile