"It was a lot nicer to bowl on than Sri Lanka," Starc said, having recorded figures of 4-71 despite an open wound in his left leg.
"It's always nice coming back home and starting a summer of cricket at home. There were a few nerves floating around the changeroom at the start of the day.
"The way we finished the day, you probably couldn't have asked for anything better."
Warner needed just 39 balls to reach 50, with all but four of those runs coming from boundaries.
The vice-captain will resume on 73, while Shaun Marsh is 29 not out."The way he can change the game with his little flourish of runs, it's what he does so well for us," Starc said.
South Africa were left seething as edges flew over their cordon like clockwork early in Warner's dig, having reviewed a confident lbw shout from Vernon Philander when he was on 17.
Ball-tracking technology suggested Warner was out but replays revealed it was a no-ball.
"It's obviously quite disappointing but there's not much we can do about that now. Tomorrow there will be opportunities to get him out," South Africa batsman Temba Bavuma said.
"Australia has the upper hand at the moment, but the game is definitely far from over."
Starc needed just four balls to remove opener Stephen Cook for a duck, with Mitch Marsh snaring a spectacular catch at gully.Josh Hazlewood dismissed first drop Hashim Amla for a duck with his seventh delivery. Not since England were 2-4 in 1998 has a side started a WACA Test so poorly.
Bavuma (51) and Quinton de Kock (84) fought back during the post-lunch session.A mistimed pull shot meant de Kock became Hazlewood's third victim, while Nathan Lyon ended Bavuma's resistance thanks to a remarkable catch from Shaun Marsh at short leg.
Starc finished South Africa's innings by skittling the stumps of Dale Steyn, having also accounted for Philander and skipper Faf du Plessis.Australia missed chances to run de Kock out on 52 and 61 but, otherwise, it was a polished performance in the field.
Match centre with scorecard, wagon wheel and Manhattan/Worm
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