code: function checkVariable(i) {
    let l;
  
    if (i >= tokensLength || tokens[i].type !== TokenType.CommercialAt) return 0;
  
    if (tokens[i - 1] &&
        tokens[i - 1].type === TokenType.CommercialAt &&
        tokens[i - 2] &&
        tokens[i - 2].type === TokenType.CommercialAt) return 0;
  
    return (l = checkVariable(i + 1) || checkIdent(i + 1)) ? l + 1 : 0;
  }
docs: Check if token is part of LESS variable
  @param {Number} i Token's index number
  @returns {Number} Length of the variable