It sounds like a Modal window would probably be helpful. I'm not an expert on Tk, but some quick searching shows Tk::Dialog, Tk::DialogBox, and several posts on PM, such as Tk Modal Window or the replies to unswitchable windows in perl-tk.

If I have not misunderstood your question, I think you can play with: $window->focus and iconify deiconify raise or withdraw and state (to query the current state) all methods of Toplevel methods.

An example available here

L*

Take a look at Tk: Binding Events and Callbacks. Your post is a bit sketchy on details, making a definitive answer difficult; however, Tk::after and Tk::fileevent look to be likely candidates for what you might want; other items in that section may also be useful.

I've written a number of posts over the years which may be relevant to your needs. In many cases I've included fully working scripts. There may be something there to suit your needs or which you can adapt as necessary. You can use this preloaded search (if you're unfamiliar with Super Search, that just preloads the search parameters: click "Search" to get the results).

$mw->Busy;

$mw->Unbusy;

Although, by default the GUI shouldn't be responsive while downloading

Thank you for the suggestions! The GUI does remain reactive because I use $mw->update; while downloading the file in order to update a Progressbar.

I opted for a quite easy solution which shows a top window with a grab until the download process is completed.

    my $tl = $mw->Toplevel( -title => 'WAIT' );
    $tl->resizable( 0, 0 );
    $tl->transient($tl->Parent->toplevel);
    $tl->protocol('WM_DELETE_WINDOW' => sub {});   
    $tl->grab;
    my $image_file = "wait.jpg";
    my $splashphoto = $tl->{Photo} = $tl->Photo(-file => $image_file);
    $tl->Label(-image => $splashphoto, -bd => 0)->pack(-fill => 'both'
+, -expand => 1);
[download]