Regarding a crossword

Question

Down

1. any of bcbbbccccbc ccbcbcccbcbcca ba ccca ca but none of a bcaa
2. any of aaaaaaaaac aaaaaaaaaaaa a2aaaaaa a2ac but none of 2aaaac a2aaaacc a22ac
3. any of 234cb 234b 23444444cb 234444444b but none of 24cb 24b 2cb 3cb 23cb 234ccb

Across

4. either of abb abbb but none of abbbb ab aabb
5. either of ]abc ]abbbbc but none of ]ac ]bc ]ab abc ]]abc
6. either of abca a but none of aa aba cba abba bcca

Answer 1

I think I solved it

The strings of characters in the clues seem like they can be described by regular expressions.

  [   a   2
a b { 2 , 3 } 
  c   ?   4
( ] ) a b + c
  +   +   c
( a b c ) ? a
  ?   ?   b

Down
1 [bc]+a? (at least one of b or c (or mixed), then optional a)
2 a2?a+c? (a, then optional 2, then at least one a, then optional c)
3 234+c?b (23, then at least one 4, optional c, then b)
Across
4 ab{2,3} (a, then exactly 2 or 3 b's)
5 (])ab+c (], then a, then at least one b, then c)
6 (abc)?a (optional abc, then a)

The cell where 3 and 6 meet could also be a * and satisfy the conditions.

I liked this puzzle, I've never seen anything like it. The only improvement I can see is if you made it have only one solution (maybe by adding more negative test cases).