A method and system automatically and dynamically updates the design of perforation lines in a package design file. It identifies an edge between two facets to which a perforation line is to be applied, determines a length of the edge, and uses the length of the edge and a default cut segment length to determine a number of cut segments that will be included in the perforation line. The method and system also may determine a phasing for the perforation line to ensure that the ends of the line are either a cut or spacer, depending on the desired function or placement of the line.