import type { UIO } from "../Effect/effect";
import type { FiberRef } from "./fiberRef";
/**
 * Atomically modifies the `FiberRef` with the specified function, which computes
 * a return value for the modification. This is a more powerful version of
 * `update`.
 */
export declare function modify<A, B>(f: (a: A) => [B, A]): (fiberRef: FiberRef<A>) => UIO<B>;
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