my $frame = Wx::Frame->new(
        undef, -1, 'Test', wxDefaultPosition, wxSIZE(400,500)
    );
   $frame->SetAutoLayout(1);
   my $q = Wx::WidgetMaker->new(-parent => $frame);
   my $pagesizer = Wx::BoxSizer->new(wxVERTICAL);
   
   foreach(@exts) {
      my $rowsizer = Wx::BoxSizer->new(wxHORIZONTAL);
      
      my $control = $q->checkbox(
           -name => 'color_checkbox',
           -checked => 'checked',
           -label => $_,
      );
      push @controls, $control;         # <== @controls global definiert
      $q->print($control, $rowsizer);
      $pagesizer->Add($rowsizer);
   }
   my $rowsizer = Wx::BoxSizer->new(wxHORIZONTAL);
   my $control = $q->submit(
        -name => 'color_button',
        -value => 'Oeffnen',
   );
   EVT_BUTTON($frame, $control, \&getExts);
   $pagesizer->Add($rowsizer);
   $q->print($control, $rowsizer);
   
   $frame->SetSizer($pagesizer);
   $pagesizer->SetSizeHints($frame);

   $app->SetTopWindow($frame);
   $frame->Show(1);

   sub getExts {
      my ($this, $event) = @_;
      foreach(@controls) {
         print Dumper \$_;
      }
   }

sub save_selected {
    my @check_boxes = @{ shift; };
    my $doc_nr = &Kephra::Document::_get_current_nr;
    for ( 0 .. $#check_boxes ) {
        if ( ref $check_boxes[$_] ne '' ) {
            if ( $check_boxes[$_]->GetValue ) {
               
 ...
            }
        }
    }
        ...
}