$usetitem(<array> <item#> <data>)

This function creates a new cell in the specified array. If the array does not exist, the client will try to create it. Unlike setitem, this function does not immediately resort the array. The actual resort will occur the next time you fetch an item from the array. This makes it very efficient to add very many values to an array.

-2    could not find item number, or item number too large
-1    could not find array, or item number not 0 for new array
 0    existing item was overwritten
 1    new array created
 2    new item number added to existing array