In IC615 (and IC614) you can directly reference the name of the output as a variable. In IC5141 however, you'd have to make the output have an assignment. So for example, rather than having:
O_1 : someFunction()
you'd have to do:
O_3: min(O_1 O_2)
note that you have to ensure that the outputs are in the right order - so that any variables are defined before they are used (in IC614/IC615 this is done automatically so that dependent expressions are evaluated in the correct order).