export function rindex(str: string, substr: string, position?: number): number {
  //      discuss at: https://locutus.io/perl/rindex/
  // parity verified: Perl 5.40
  //     original by: Kevin van Zonneveld (https://kvz.io)
  //          note 1: Returns the last index of substr in str, or -1 when not found.
  //       example 1: rindex('hello hello', 'lo')
  //       returns 1: 9
  //       example 2: rindex('hello hello', 'lo', 8)
  //       returns 2: 3
  //       example 3: rindex('hello', 'x')
  //       returns 3: -1

  const source = String(str)
  const needle = String(substr)

  if (position === undefined) {
    return source.lastIndexOf(needle)
  }

  const from = Math.trunc(Number(position))
  if (!Number.isFinite(from)) {
    return source.lastIndexOf(needle)
  }

  return source.lastIndexOf(needle, from)
}