@insert(t:tab, i:numeric, v:value)
@insert(m:map, k:val, v:value)
@insert(t, i, v) inserts “in place” the value v into the tab t
after the index i (tab's elements are indexed starting with 0).
If i is negative, the insertion take place in front of the tab.
If i >= @size(t) the insertion takes place at the end of the tab.
@insert(m, k, v) inserts “in place” a new entry with value v under
key k in the map m. If the entry already exists, the current value
is replaced by v. See @add_pair
Notice that the form is also used to include a file at parsing time. See section file structure.