sets an element in an array to a value. If the element doesn't exist yet in the array, the array is resized to hold the element. So, be careful. If you give an index value of 1000, then you'll suddenly have an array with 1000 elements stored in memory. Index values start at ZERO.
#VAR a %array(1,"test","hello") #NOOP %arrset(a,5,"new") #VAR a