Winchester, 29, is in his sixth season. He has 30 goals and 26 assists in 304 career games.
Perrault, 27, has spent most of this season with AHL Manitoba.
The Blues were 13th in the Western Conference with 65 points, seven points out of the final playoff spot. Before Monday's deal, St. Louis unloaded forward Brad Boyes to Buffalo, and defensemen Eric Brewer and Erik Johnson to Tampa Bay and Colorado, respectively. Brewer had been the team captain.
Information from ESPN.com's Pierre LeBrun and The Associated Press was used in this report.