When you offer employee perks, it’s critical to make clear whether the program is a vested benefit or a company bonus that is subject to change or cancellation. Former Hewlett-Packard engineer Mark G. Leonard is suing the high-tech giant, claiming that it cancelled a program to provide thousands of retirees lifetime rebates on its products, including computers, scanners and printers. Current HP workers still get the product rebate. But Leonard, who worked for HP for 23 years before retiring in 1999, claims he stopped receiving the 10% discount when he was reclassified as an employee of HP spin-off, Agilent Technologies Inc. in 1999, even though Agilent didn’t yet exist when he retired. Leonard is asking a Santa Clara county court to force the firm to restore the rebate program for 3,800 other HP retirees who were similarly reclassified. In response to the lawsuit, HP said that the employee product rebate program is not a vested benefit and is subject to change at any time.