1=>a
21 a
31 a | a
40 b
5=>a|b
61 a
71 b
81 a | b
90 a{0}
100 b{0}
11=>a | b | a
121 a
131 b
141 a | b
151 b | a
161 a | b | b
171 a | b | a
181 b | a | b
19=>a,a
201 a,a
210 a
220 a,a,a
23=>a{0,3}
241 a{3}
251 a
261 a,a,a
271 a{1,3}
28=>(a|b){0,4}
291 a
301 b
311 a,b
321 a,b,a,b
330 b,a,b,a,b
341 b,a{1,3}
351 a{1,3},b
360 a{1,3},b,a
370 a{1,4},b
380 a{0,5}
391 (b|a){0,4}
400 (b|a){0,4},a
411 (a,b){0,2}
421 (a,b){0,1},b
43=> a*
441 a
451 a?
461 a+
471 a*
481 a{0}
49=> a+
501 a
510 a?
521 a+
530 a*
541 a?,a
551 a,a*
561 a*,a
571 a?,a*,a
581 a*,a?,a
59=>(a|b)*
601 a
611 b
621 a,b
631 a,b,a,b
641 (b|a){0,4}
651 (b|a){0,4},a
661 a*
671 b*
681 (a|b)*
691 a{1,3}
701 b,a{1,3}
711 a{1,3},b
721 a*,(a|b)*
731 a*,b{2,5}
741 a*,(a|b)*,b{2,5}
75=>(a|b)+,(c|d)
761 a+,c
770 a*,c
781 a,c
791 a,b*,a*,c
80# more complex
81=>(a|b),(a|c){0,100}
821 a{0,100},(a|c)
830 a{0,101},(a|c)
84# the example from cmsmcq at extreme markup 05
85=>(a, ((b, c, d){0,5}, e{0,1}){0,4}, f)
861 (a, b, (c, d, b){2,3}, c, d, e, f)
87