Post-multiply another system or a scalar
Handles multiplication of systems in the sense of a frequency domain multiplication. That means, given two systems E1(s) and E2(s), their multiplication, H(s) = E1(s) * E2(s), means that applying H(s) to U(s) is equivalent to first applying E2(s), and then E1(s).
For SISO systems the order of system application does not matter. However, for MIMO systems, where the two systems are matrices, the order above ensures standard Matrix multiplication rules apply.