Not really. Most data preparation is done outside of IML by using the DATA step or SQL. There is nothing in SAS/IML that matches their power and convenience.
You can, of course, use the LOC function, in conjunction with subscripting and concatenation, to match and merge rows of matrices. The UNIQUE-LOC technique is often used to combine data by matching categories. The EXPANDGRID function is a kind of joining operation, since it is a Cartesian product operation.