function findInterpolation(string, startIndex) {
    const interpolationRegex = /#{(.*?)}/g;
    const results = [];
    // Searching for interpolation
    let match = interpolationRegex.exec(string);

    startIndex = !isNaN(startIndex) ? Number(startIndex) : 0;
    while (match !== null) {
      results.push({
        source: match[0],
        operators: findOperators({
          string: match[0],
          globalIndex: match.index + startIndex
        })
      });
      match = interpolationRegex.exec(string);
    }

    return results;
  }
Takes a string, finds all occurrences of Sass interpolation in it, then
finds all operators inside that interpolation

@return {array} An array of objects { string, operators } - effectively,
   a list of operators for each Sass interpolation occurrence