/**
 * This splits a string on a top-level character.
 *
 * Regex doesn't support recursion (at least not the JS-flavored version).
 * So we have to use a tiny state machine to keep track of paren placement.
 *
 * Expected behavior using commas:
 * var(--a, 0 0 1px rgb(0, 0, 0)), 0 0 1px rgb(0, 0, 0)
 *       ─┬─             ┬  ┬    ┬
 *        x              x  x    ╰──────── Split because top-level
 *        ╰──────────────┴──┴───────────── Ignored b/c inside >= 1 levels of parens
 *
 * @param {string} input
 * @param {string} separator
 */
export declare function splitAtTopLevelOnly(input: any, separator: any): any[];