"We have a tribute to him," Spelling told host Andy Cohen about the new dramedy, which starts Wednesday on Fox.
The show features the former stars of 90210 playing heightened versions of their real selves as they are supposedly working on bringing the original show back.
"It was delicate," Garth said of how Perry's death will be handled in BH90210. "It was impossible to find the right way to do it."
The actresses confirmed their new show was in development when Perry was still alive and they wanted him to be part of it "in some capacity," even though he was committed to his latest project, Riverdale.
"When we did the meetings, he was on a conference call from Vancouver," Spelling said. "He was in support of it."
Spelling and Garth also said they were happy Shannen Doherty -- who was fired from the original series -- is back for the revival.
"It wouldn't be the same without her," they both said, noting Doherty is "integral" to the 90210 history.
Garth admitted Spelling often acted as peacekeeper when things grew tense between Garth and Doherty on the 90210 set.
"We were young and so stupid," Garth laughed, remembering how they almost came to blows one time when Doherty pulled her skirt up.
Fortunately, people held them back and no one got hurt.
"We're both strong, Aries women and we don't back down no matter what," Garth said.
Spelling admitted she was shaking in her trailer during the time of the confrontation.
Perry died on March 4 following a stroke. He was 52.
Doherty recently guest starred on the season premiere of Riverdale as an homage to Perry.
Spelling and Garth announced Monday that they are planning a live talk-show tour across the United States.