用三个线程，第一个线程负责mailing-list和template的处理，就是把mailing-list里人的邮箱地址和人名之类的按照要求填进template里的模板里，

第二个是负责处理template里的空格的，多于一个的连续空格要变成一个，每行最后的空格要去掉，每行开头不能有空格

第三个就是处理？，。等标点符号后要有两个空格，，而且命令行输入一个X，每行超过X个字节后就要自动换行

输出就是要把mailing-list里的人的信息填入tempate后输出到文件mail00001，mail00002，·····等有几个人就要有几个文件-– A sample substitution file, named mailing-list. Each addressee begins with a line

that says “NEW”.

– A template letter (template). Each substitution rule will contain a colon　if it

doesn’t, ignore it.

– Two sample letters, the results of applying the substitution rules to the template

letter (sample1 and sample2).

Mail Generation Steps

•　Step 1: Convert all tags in the template to their plaintext equivalent, according to the

substitution rules in the mailing-list. Tags will be nonempty strings of characters

surrounded by a pair of ^ characters. Tags that do not match any substitution should

be removed, i.e., replaced by the empty string. If you encounter the string “^^”, it is

not a tag, but should be replaced by a single ^. A ^ which is unmatched on the same

line should be reported as an error, and the program terminated.

•　Step 2: Eliminate all extraneous spaces. Specifically:

– spaces at the beginning of a line should be removed

– spaces at the end of