In providing perforation uniformity both in the spacing between multiple rows of perforations in sheet material and in the spacings among perforations within each row, a common laser beam is shared among the rows, being directed to the sheet material through a common focusing element for each adjacent pair of rows. In conducting the laser beam to each such common focusing element, a pair of modified beams is derived from the laser beam, each modified beam having light ray content divergent about an axis of symmetry thereof which is parallel to the optical axis of the focusing element.