sub simple_nudge {
    my ($w)    = @_;
    my $mw  = $w->toplevel;
    my $geo = $mw->geometry;
    ($geo =~ /^(\d+)x(\d+)[+](\d+)[+](\d+)$/) or return;
    my ($w0, $h0, $x, $y) = ($1, $2, $3, $4);

    # Grow the main window by 1 pixel, then restore its original size
    my ($w1, $h1) = ($w0 + 1, $h0 + 1);
    $mw->geometry("${w1}x${h1}+${x}+${y}"); $mw->update;
    $mw->geometry("${w0}x${h0}+${x}+${y}"); $mw->update;
}