use Tk;

my $mw = tkinit;
$mw->overrideredirect(1);
$mw->Label(-text => 'move window')->pack;
$mw->Button(-text => 'Exit', -command => sub {exit})->pack;

my ($x, $y);

$mw->bind('<B1-Motion>', sub {
my ($x2, $y2) = $mw->pointerxy;
if (defined $x) {
printf("move (%d, %d) => (%d, %d)\n", $mw->rootx,
$mw->rooty, $mw->rootx+$x2-$x, $mw->rooty+$y2-$y);
$mw->geometry(sprintf("+%0d+%0d", $mw->rootx+$x2-$x,
$mw->rooty+$y2-$y)) if defined $x;
}
($x, $y) = ($x2, $y2);
});

# Reset starting-coordinates
$mw->bind('<Motion>', sub {($x, $y) = (undef, undef)});

MainLoop;
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