Step 3下面的put statement如何解读？为什么有多个引号？
谢谢~


data _null_;
merge Out1
Out2(rename=(Length=Length2))
end=last;
by Name;
file "c:\books\tasks\Combined.sas";
/* Step 1 */
if _n_ = 1 then put "Data Combined;";
/* Step 2 */
L = max(Length,Length2);
/* Step 3 */
put " length " Name " $ " L 3. ";";
/* Step 4 */
if Last then do;
put " set Name1 Name2;";
put "run;";
end;
run;