1  Regexp: (a|b{0,3}){0,1}
 2  a: Ok
 3  aa: Fail
 4  b: Ok
 5  bb: Ok
 6  bbb: Ok
 7  bbbb: Fail
 8  ab: Fail
 9  ba: Fail
10  Regexp: ([0-9]{0,3}|([0-9]{0}|[0-9]{0,3})){0,3}
11  0: Ok
12  00: Ok
13  123: Ok
14  abc: Fail