/**
 * The `!ENV ${VAR[:default]}` manifest marker grammar the platform reads: a string leaf
 * that begins with the `!ENV ` prefix (the tag and exactly one space) references an
 * environment variable by name, never its value. A variable name carries no `{`, `}` or
 * `:`; an optional `:default` follows it.
 */
/** The prefix that makes a string leaf an `!ENV` marker. */
export declare const ENV_MARKER_PREFIX = "!ENV ";
/** The reference of a single-reference marker leaf. */
export interface EnvRef {
    readonly key: string;
    /** The `:default` text (without the leading colon); absent for a bare reference. */
    readonly default?: string;
}
/** The reference of `value` when it is exactly `!ENV ${KEY}` or `!ENV ${KEY:default}`, else `null`. */
export declare function parseEnvMarker(value: unknown): EnvRef | null;
/**
 * The marker referencing `key`, carrying `defaultValue` when given. Throws when
 * {@link parseEnvMarker} would not read the marker back as `(key, defaultValue)`: a name is
 * non-empty and carries no `{`, `}` or `:`; a default is non-empty and carries no `}`.
 */
export declare function formatEnvMarker(key: string, defaultValue?: string): string;
/** Every variable name any marker leaf anywhere under `value` references. */
export declare function collectEnvRefs(value: unknown): Set<string>;
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