st: Keywords in programming

["Zhuo Chen" <zchen1975@hotmail.com>]

I am reading an ado file written in Stata V5, there is a few keywords I 
couldn't really uderstand, i.e., _crceprs, could anyone tell where should I 
look for a list of these keyword or commands?
I am also having trouble with

local if "opt",

is this this going to contradict the "if" used in Stata?

Thanks,

Adam
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