module toy;

input in[3:0];
input longop;
output out;

s01 = in[0] & in[1];
s23 = in[2] & in[3];

s01_muxed = (longop) ? s01 : ~s01; // or, (longop == s01)

s01_muxed_flopped <= s01_muxed;
s23_flopped       <= s23;

s0123 <= s01_muxed_flopped & s23_flopped;

longop_flopped <= longop;

out = (longop_flopped) ? s0123 : s01_muxed_flopped;

endmodule // toy