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代码说明：

  输入圆的半径求周长和面积。程序由三个函数组成：主函数进行输入输出和函数调用，perimeter函数求周长，area函数求面积。(Enter the radius of the circle circumference and area requirements. Program consists of three functions: the main input and output functions and function calls, perimeter function evaluation perimeter, area function for the area.)