Probably something like this to set column 1 to column 0:
set array at (1,0) to array.at(0,0)
set array at (1,1) to array.at(0,1)
set array at (1,2) to array.at(0,2)
set array at (1,3) to array.at(0,3)
set array at (1,4) to array.at(0,4)
...
set array at (1,array.height-1) to array.at(0,array.height-1)
But that just screams "use a loop", so...
repeat array.height times
---set array at (1,loopindex) to array.at(0,loopindex)