The "wildcard bins" in SV useful for covering addresses/register coverage with specific

 This is useful in finding register bit specific coverage
 If reg1 is a 32 bits wide and we were interested in LSB [3:0] in combine with msb [31]=1

  REG1_BITS_CP : coverpoint reg1 {  
                                     wildcard bins ={32'b1000_0000_0000_0000_0000_0000_0000_????};
                                 }

So with this cover point you will get  16 bins ,32'b1000_0000_0000_0000_0000_0000_0000_0000,32'b1000_0000_0000_0000_0000_0000_0000_0001 to 32'b1000_0000_0000_0000_0000_0000_0000_1111.