swift官方文档中的switch中case let x where x.hasSuffix("pepper")是什么意思？

let vegetable = "red pepper"

switch vegetable {
    
    case "celery":
    
        let vegetableComment = "Add some raisins and make ants on a log"
    
    case "cocumber", "watercress":
    
        let vegetableComment = "That would make a good tea sandwich."
    
    case let x where x.hasSuffix("pepper"):
    
        let vegetableComment = "Is it a spicy \(x)?"
    
    default:
    
        let vegetableComment = "Everything tastes good in soup.123321"
}