You're seeing the 2004 Oliver Perez. After that season, Pittsburgh coaches tried to change his release, I believe to prevent injury. He completely lost his control. Rick Peterson put him back to his old mechanics, and it's really paying off.
Remember Game 7 of the NLCS? We were supposed to lose because of our starter in that game. It was Perez, and he pitched a gem... We did lose, but it was the bullpen and dead bats.
The Philly outing was odd. He retired the first four batters, then had some walks. He only pitched 2 2/3 innings because he was walking them in bunches, but he only gave up one hit. I think that game is going to be an aberration. I don't expect him to continue to perform like he has against the Braves, but he does have that much potential.