$top->Busy(-recurse => 1);
# call your subroutine
$top->Unbusy;
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If your subroutine may die, then it's better to have the subroutine call in an eval { }, otherwise your application will stay unresponsive. With newer Perl/Tks (>=804) you can use this shortcut instead:

$top->Busy(\&your_subroutine, -recurse => 1);
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