You can do something like this in the button definition: 
   $QuitButton = $TopFrame->Button(
     -text     => 'Quit',
     -relief   => 'raised',
     -cursor   => 'pirate',
     -command  => sub { 
        my $str = "Are you sure you want to Quit?";
        if ( &GUI_PopupQuery("TOOL","QUIT","Cancel",$str )) {
           ## add code here to close any open windows...
           $MW->destroy();
        }
      });

[download]

You need then a subroutine to create a popup window, and receive the arguments passed above, and then return either 1 or 0, depending on the results of the the query. Note that you should probably do additional things, like make the popup do a toplevel grab, so that it has grabbed the input focus, bind <RETURN> to the default function, which would be NO presumably, then make the toplevel do a wait...

Here's a stripped down version of this that could work. In my code, I pass the affirmative and negative response strings to the generic popup subroutine, so I can call it with a variety of queries. This is pared down code from the actual source that I copied it from, so hopefully it's sufficient in itself, but you may need to add tweaks here and there, for padding, fonts, window features, etc. The toplevel window is in $topLevel: 

sub GUI_PopupQuery {
my ($title, $AffirmativeText, $NegativeText, $str) = @_;
   print("\a");  ## beep
   my ($topLevel, $topFrame, $botFrame, $labelFrame,
       $CancelButton, $OKButton);

   $topLevel = $MW->Toplevel();
   $topLevel->wm('transient', $MW);
   $topLevel->geometry('+200+200');
   $topLevel->title("$title");
   $topLevel->resizable(1, 0);

  ## FRAMES...
   $topFrame =
      $topLevel->Frame(-height => 120,
                       -width  => 150,
                       -relief => 'ridge',
                 )->pack(-side => 'top',
                         -fill => 'both',
                         -expand => 1);

   $botFrame =
      $topLevel->Frame(-height => 120,
                       -width  => 150,
                       -relief => 'ridge',
                       -borderwidth => 2,
                 )->pack(-side => 'bottom',
                         -fill => 'both',
                         -expand => 1);

   ## TOP FRAME ELEMENTS...
   $topFrame->Frame(   -height => 20,
              )->pack(-side => 'top',
                      -pady => 5,
                      -fill => 'both',
                      -expand => 1);

   $labelFrame =
      $topFrame->Frame(-height => 50,
                       -width  => 50,
                       -relief => 'flat',
                       -borderwidth => 2,
                 )->pack(-side => 'top',
                         -fill => 'both',
                         -expand => 1,
                         -pady => 5);

   $labelFrame->Label(-text   => $str,
                     -width  => 60,
                      -relief => 'groove',
                      -padx   => 6,
                      -pady   => 6,
                      -bg     => 'red3',
                      -fg     => 'white',
                )->pack( -anchor => 'center',
                         -fill => 'both',
                         -expand => 1);

 ## BOTTOM FRAME ELEMENTS...
   my $botButtonFrame =
      $botFrame->Frame(-height => 120,
                       -width  => 150,
                       -relief => 'ridge',
                       -borderwidth => 2,
                 )->pack(-side => 'bottom');

   $OKButton =
      $botButtonFrame->Button(-text => $AffirmativeText,
                       -padx     => 8,
                       -pady     => 8,
                       -width    => 8,
                       -command  => sub
                       { $returnval=1;
                         $topLevel->grabRelease;
                         $topLevel->destroy();
                       },
                       -font     => $fontB
                      )->pack(-side =>'left');

   $CancelButton =
     $botButtonFrame->Button(-text => $NegativeText,
                       -padx     => 8,
                       -pady     => 8,
                       -width    => 8,
                       -command  => sub
                       {  $returnval=0;
                          $topLevel->grabRelease;
                          $topLevel->destroy();
                       },
                      )->pack(-side => 'left');


   # Bind the "OK" button to exit when "<return>" 
   # is pressed
   $topLevel->bind("<Return>",
              sub{
                $topLevel->destroy();
                $returnval=1;
              } );


   $topLevel->waitVisibility();
   $topLevel->waitWindow();

   return $returnval;
}

[download]

Hope this may be useful for you...

Cheers!
Cadphile...

In reply to Re: Cancel close of mainwindow in Tk on Windows by cadphile
in thread Cancel close of mainwindow in Tk on Windows by smaclach

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