Regexp: ((a|b|\p{Nd}){1,2}|aaa|bbbb){1,2}
bab: Ok
aaca: Fail
aaabbbb: Ok
a0b: Ok
aa0aaa: Fail
b0aaa: Ok
Regexp: (\d{1,3}\.){3}\d{1,3}
1.2.3.4: Ok
1.22.333.44: Ok
1.2.3: Fail
1..2.3: Fail