There was much more to him than the spitball.
He was a horse. He didn't become a full-time starter until he was 27 years old, but over the next fifteen seasons, through his age 41 season, his average year was 18-13, 2.87, pitching 285 innings and completing more than half of his starts. Year after year after year. You'll take that on your team. He never had a bad season - at least not until he had turned 42 and had declined to the level of roughly league average inning eater. He threw strikes and he kept the ball in the yard.
Perry was notorious, if not legendary, for the mind games he played with hitters his whole career. His mid-career autobiography was entitled Me and the Spitter and it blithely catalogues all the various ways Perry knew how to doctor a baseball, tricks he claimed to have learned from Bob Shaw, who was himself a notorious spitballer. Before every pitch, Perry fidgeted endlessly on the mound, touching various parts of his head and his neck and his uniform. It made the opposition crazy, but no one ever caught him until August 1982, by which time he'd already won 300 games.
He was a redneck, a country boy from a very small town in North Carolina called Williamston - back home his name was pronounced "Gay-lerd" (rhymes with "bird".) His big brother Jim preceded him to the majors, and also had trouble establishing himself as a full-time starter. Jim spent the first ten years of his career as a swingman before finally getting his chance and giving the Twins a couple of 20 win seasons.