It creates a new list with the elements of the base list whose indices are in the argument list.
If the argument list contains two indices [a,b] then
SUBLIST returns the list of elements from index a to index b (included). If the argument list contains more than two indices, the result of
SUBLIST contains all the elements at the specified indices, with possible duplicates.
Negative indexing is allowed, with negative index effectively refering to index + size.
Since 2.1 a new signature allowing the step to be defined has been introduced. Instead of specifying a list has range, you can put the start, end (optional) and step (optional) as LONG values.