我从网上下载到一个STATA的ado程序，程序如下：

*. simpbin0 dvf, bin(varlist) exog(varlist)

/* The model is D=I(v+x'B+e>0), E(ez)=0,
conditional density of v is f .*/

*set trace on
cap pro drop simpbin0
pro def simpbin0, eclass
version 8.0

local varlist "required existing min(3) max(3)"
local if "optional "
local options "bin(string) exog(string)"
parse "`*'"

preserve

tokenize "`varlist'"                  
gen `1'star=(`1'-(`2'>=0))/`3'

di in g "                "
di in g "Based on the known conditional density of `2', f(`2'|.)"
di in g "                "
di in g "`1'star is constructed as (`1'-(`2'>=0))/ f(`2'|.)"

ivreg `1'star (`bin'=`exog'), robust
drop `1'star
end

请教大家，标红的语句该如何解读呢，除了设置局部宏，还有什么其他的作用吗？并且这个程序没有args 或者syntax语句的设置，如何保证运行时的格式呢？谢谢各位啦。