use constant { alpha => 0.1, }; my ($prev_x, $prev_y) = (0, 0); while (<>) { my ($t, $x, $y) = split; $x = $prev_x + alpha * ($x - $prev_x); $prev_x = $x; $y = $prev_y + alpha * ($y - $prev_y); $prev_y = $y; print "$t $x $y\n"; }