Confused about lifetime anchoring with chained "appending" builders

i have a “path” type that has a builder API that looks like

extension Path
    @inlinable public static
    func / (prefix:Self, last:String) -> Self
        var prefix:Self = prefix
        return prefix

(hopefully the layout of Path should be obvious, but it is essentially a wrapper around a [String] array.) but apparently prefix lives for the entire duration of a function call, so / has linear complexity even if it is being used like:

let path:Path = "first" / "second" / "third" / "fourth"

which makes the whole thing quadratic in number of path components.

what is the best way to get this to actually work like an array literal? (i am not using array literal syntax because we cannot statically assert the array literal has at least one path component.)

Variadics, with one non-variadic argument at the head. Or wait for the language to have finer-grained ownership controls, or only provide a mutating /=.