Syntax

4x1_MUX {[Subcircuit-label-n] [label-n]}
# where, the Subcircuit labels are D3, D2, D1, D0, S and Y
# All Subcircuit labels are mandatory
# Order is arbitrary

Example

4x1_MUX D3 A D2 B D1 C D0 D S1 E S0 F Y G 
# Order of the Subciruit labels doesn't matter

This block selects one from the four Data inputs, binary encoded from zero to three, based on the logic levels at the Select lines/Select inputs and passes to the output, while the other Data inputs which aren't selected, don't influence the output for that selection.