export declare function firstNonEmptyEnv(env: Readonly<Record<string, unknown>> | undefined, primary: string, legacy?: string): unknown;
export declare function envFlag(env: Readonly<Record<string, unknown>> | undefined, primary: string, legacy?: string): boolean;
export declare function envString(env: Readonly<Record<string, unknown>> | undefined, primary: string, legacy: string | undefined, fallback?: string): string;