He oversaw the scientific team led by Dr. Mason Wren onboard the starship Auriga that sought to resurrect the Xenomorph species by cloning the long-deceased Ellen Ripley, although in reality he had little involvement with the project beyond a basic managerial role. Instead, Perez focussed on the day-to-day running of the Auriga itself, a task that he conducted with extreme military efficiency and precision.
He saw Ripley as a threat to the project and thought about killing her. He was also the most passionate of the project. He also made a deal with pirates to kidnap the thirteen people that were later used to hatch thriteen of the aliens at the behest of the scientific team.
When the Xenomorphs broke out, he ordered the immediate evacuation of the Auriga. He destroyed one of the lifeboats to destroy one of the xenomorphs there that was massacring the evacuees there. He was later killed by another Xenomorph from the back, when he paid respects to the dead.