type NullOnInvalidInput = {
    nullOnInvalidInput: true;
};
type ThrowOnInvalidInput = {
    nullOnInvalidInput: false;
};
declare function UUIDtoULID(ulid: string, opts?: ThrowOnInvalidInput): string;
declare function UUIDtoULID(ulid: string, opts: NullOnInvalidInput): string | null;
declare function ULIDtoUUID(ulid: string, opts?: ThrowOnInvalidInput): string;
declare function ULIDtoUUID(ulid: string, opts: NullOnInvalidInput): string | null;

export { ULIDtoUUID, UUIDtoULID };