The 38-year-old five-time world champion trailed 4-1, before reducing the deficit to 5-3 in this best-of-25-frame clash at the Crucible Theatre.
Perry was quick out of the blocks, taking the opening frame. O’Sullivan levelled but his Wisbech opponent took the next two frames to go in at the mid-session interval 3-1 up.
O’Sullivan was in trouble when he lost the fifth frame, but he produced a 116 clearance to reduce the deficit to two frames.
The defending champion appeared to be finding fluency when he followed up with a decisive 75 to move to within a single frame of Perry.
However, a break of 99 from Perry checked the progress of ‘The Rocket’ and gave the 39-year-old the edge for when the match resumes this afternoon.
The other second round match which started yesterday saw Mark Selby establish a lead over Ali Carter, with the margin again 5-3.
Two-time beaten finalist Carter took the opener with a clinical 102 break, before Selby responded with a 38 and 84 in the second, then took the third after emerging from a safety battle.
Selby, playing close to his best, won the next two frames and with a 5-1 advantage looked set for a healthy lead. However, Carter dug in with a gritty 44 after Selby had spurned the first chance and then, after Selby failed to make the most of a fluke, rattled in a thrilling 110 for his second century of the afternoon.
Earlier, 2010 champion Neil Robertson posted the tournament’s highest break as he wrapped up a 10-2 victory in his first-round match against Robbie Williams.
The Australian left-hander and world number one, who held a 7-2 overnight lead, did not take long to wrap up victory, following a clearance of 140 with a knock of 102 as he sealed a second round match against Mark Allen.
Dominic Dale secured a first win at the Crucible since 2000 in the remaining first round tie, turning an overnight 7-2 advantage over Mark Davis into a 10-5 success.
He will face Michael Wasley, ranked 73 in the world, in the second round.