Sri Lanka captain Angelo Mathews steered his team to a fighting total of 310.
After struggling at 62 for 3, a 122-run stand between Mathews (93) and NLTC Perera (65) for the fourth wicket provided a strong foundation for the hosts to target the Pakistani pace attack in death overs.
Pakistan gave away 80 runs in the last six overs alone.
Sri Lanka captain Angelo Mathews had won the toss and was elected to bat in the rescheduled second one-day international against Pakistan in Hambantota today.
The tourists, who won the opening one-dayer at the same venue on Saturday, will look to clinch the three-match series despite the absence of two star players, Saeed Ajmal and Younis Khan.
Off-spinner Saeed Ajmal is yet to return from Australia where he underwent tests on his bowling action after being reported by the umpires during the preceding Test series, which Sri Lanka won 2-0.
Top-order batsman Younis has returned home following a death in the family and was replaced by Sharjeel Khan.
Sri Lanka made one change for a game they must win to keep the series alive, dropping batsman Dinesh Chandimal to play leg-spinner Seekkuge Prasanna.
The match was originally slated to be played in Colombo on Wednesday, but heavy rains in the Sri Lankan capital forced officials to change the venue and advance the game by a day. The third and final one-dayer will be held in Dambulla on Saturday.
