I have written a module in Verilog implementing a D flip-flop, like the following:
module d_flip_flop(q,d,clk,reset);
Now, I want to implement a 4-bit shift register using this module. So I have to execute four d flip flops in parallel inside always @(negedge clk) block. I don't know how to parallel execute four user defined modules inside always (or how to instantiate). I don't want a direct behavioral implementation of a 4-bit shift register.