Planned Partitioned Enclose r←x⊂y

This primitive or feature is planned, that is, it doesn't appear in the most recent released implementation of TinyAPL. Details may change before it is added!

x is a vector of naturals, of length either equal to or one more than the tally of y. r is a nested vector created by inserting partitions between the major cells of y as specified by x. Cells before a partition are dropped.