i'm writing a Tk applicaiton that hides its main window for a few seconds while it loads. it shows a toplevel while it waits, so my code looks something like this:

my $mw = MainWindow->new;
$mw->withdraw();
$mw->BList;
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where BList is a subclassed Toplevel. Everything works, except that, when the program loads, a window appears for a split-second and then vanishes. i assume this happens because the MainWindow is displayed for a second and then immediately withdrawn. how can i prevent this?