Tuukka Rask allowed four goals on just 22 shots in defeat.
Perreault reached his milestone with 7:18 gone in the third period. Roman Hamrlik flipped a high shot on net from the point, which Rask blocked away. But the 24-year-old fought off his checker in the slot and slid the rebound home for a 4-3 Washington lead.
Wideman scored an empty-netter from his own defensive zone to ice the game with 27 seconds remaining. Jeff Halpern won the left-circle draw to set up the insurance tally.
Eakin equalized for the Caps at 2:14 of the second, when his shot from the left wing caromed off the end boards, back into the crease and off Rask's blocker and crossed the goal line.
Only 41 seconds later, Perreault one-timed an Alexander Semin feed home from between the circles.
Seguin made it 2-2 with 7:39 left when he deked Vokoun and scored in a small space inside the left post, but Perreault broke free and beat Rask just over two minutes later to restore the hosts' one-goal edge.
Marchand then pumped home a rebound on a power play for a 3-3 game with 2:18 to go.
Ovechkin also announced that he will not attend the All-Star festivities in Ottawa this weekend...Perreault matched his career high in goals with the burst, as he totaled seven in 35 games last year...Bruins forward Nathan Horton missed the game due to a mild concussion suffered when Flyers forward Tom Sestito hit him during Sunday's game in Philadelphia...Both clubs resume their respective schedules next Tuesday, as Washington plays at Tampa Bay, and Boston hosts Ottawa.