Ensign Perez was a male Human Starfleet officer who lived during the mid-23rd century. He served in the operations division aboard the USS Enterprise under Captain James T. Kirk as one of the ship's security officers in mid-2270s.
During that time, he responded to an intruder alert in Ilia's quarters. During the conversation between Kirk, McCoy, and the Ilia probe, Perez inquired what was meant by the term "carbon unit." (Star Trek: The Motion Picture)