st: version 5.0 to version 9.2

["Raphael Fraser" <raphael.fraser@gmail.com>]

Can any one convert the following code to Stata 9.2 syntax? I am not
sure what the "@" means.

version 5.0
for temp* : gen r@=cond(@==1,res,.)
for rtemp*: by `3': replace @=sum(@)
for rtemp*: by `3': replace @=@[_N]
for rtemp*: replace @=cond(@==0,.,@)

Regards,
Raphael
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