I need regexp to match string build from several groups (A is any letter, 9 is any digit): group 1 regex [A-Z]{1,2}[0-9]? A A9 AA9 group 2 regex [A-Z]{1,3}[0-9]? A AA AAA AAA9 group 3 regex [A-Z]{2,3}[0-9]?[A-Z]? AAA AA9 AA9A group 4 regex [0-9]{1,2}[A-Z]{1,2}[0-9]? 9A 9AA 9A9 99A9 Not each group must be present but there must be all in correct order - I mean (digit is group number): 1 12 123 1234 So if there is present group 3 there must me all preceding groups present also. As there are four groups (can be more), so alternative like ^[A-Z]{1,2}[0-9]{1}|[A-Z]{1,2}[0-9]{1}\s{1}[A-Z]{1}[0-9]?$ is not the best option as it would be complicated and difficult to maintain. Is there any solution with groups or something? The order of groups is important.