Lahiri, lying tied 8th overnight dropped to tied 23rd after a round of 73, while Chawrasia, lying close to the bottom after 16 holes in the second, picked himself with two closing birdies for a 71. Chawrasia is now tied 45, almost the same where he had started.
Lahiri's 73 was his first over-par round in the last 14 rounds at TPC Kuala Lumpur, a period during which he won the Malaysian Open and finished tied 3rd at 2016 CIMB.
Perez had four birdies in a row from second to sixth and added two more on eighth and ninth for an incredible six-under second nine after starting from the 10th.
Chasing Perez was Xander Schauffele, who carded another fine round of 67, that included an eagle, a par, a birdie and a bogey in a four-hole stretch from third to sixth. He moved him to 12-under and sole second.
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While Perez won the OHL Maykoba in the wrap-around segment of the previous season, Schauffelle won the Greenbrier and ended the rookie year with a win at the Tour Championships, which was his last start before coming to CIMB for a maiden appearance.
Earlier during the rain stoppage, he had said, "Rain delays is something we are used to in Malaysia."
But possibly the early momentum was lost when players sat out for a long period, waiting for the weather to clear.
Lahiri had just the kind of a start he would have wanted with a birdie on the first and another one ready to be holed on second. That's when play was stopped and did not resume till four hours later. When it did, Lahiri missed the birdie putt but made up with back-to-back gains on fourth and fifth.
Chawrasia had a bogey on second, but before the rain came in he found a birdie on fourth and was even. A birdie on sixth, following a nice approach shot, saw him under par. The 11th gave him pain for the second day running as he followed up his first day's double with a bogey today. Making it worse was a bogey on 12th.
Perez, at 41, made his first Tour Championships last month, and on the 2016-2017 PGA Tour season he won once and claimed six other top-10s. He is bidding to become the oldest champion in the CIMB Classic.