Madchen, who plays Alice Cooper in the show, shared a snap on Instagram of herself and other members of the cast and crew taking part in a table read for the first episode of season four.
"There was nothing but love, memories and mourning for our beloved Luke as we honour him in our first episode back," she wrote, adding the hashtags, "#wemissyouluke #inmemoriam #riverdale #S4 #tableread".
Perry was in the middle of production of the third season of the show in March when he had a massive stroke and died, aged 52.
Aguirre-Sacasa previously revealed that the first episode of the new series would pay tribute to Luke, who starred as Fred Andrews in the programme.
"Probably the most important episode of #Riverdale we'll do this year, if not ever. A tribute to our fallen friend. Thankful for this opportunity to honour Luke & Fred," he tweeted last month.