/**
 * Expression Utilities
 *
 * Shared helpers for extracting variable references from JS/condition expressions.
 * Used by skillValidator (load-time checks), skillExecutor (runtime evaluation),
 * and CLI validate command.
 */
/**
 * JavaScript built-in identifiers that should be ignored when extracting
 * user-defined variable references from condition expressions.
 */
export declare const JS_BUILTINS: Set<string>;
/**
 * Extract root variable names from a JS-like expression string.
 *
 * Examples:
 *   "performance_summary.data[0]?.app_jank_rate > 10" => ["performance_summary"]
 *   "jank_stats.data.find(j => j.jank_type)"          => ["jank_stats", "j"]
 *   "typeof foo !== 'undefined' && bar > 0"            => ["foo", "bar"]
 *
 * Variables that appear after a `.` (property access) are filtered out.
 * JS keywords and built-in globals are excluded via {@link JS_BUILTINS}.
 */
export declare function extractRootVariables(expr: string): string[];
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