3 . 5  . . .  7 . 6
. . .  2 . 7  . . .
1 . .  . . .  . . 8

. 6 .  . . .  . 1 .
. . .  . 4 .  . . .
. 5 .  . . .  . 4 .
 
7 . .  . . .  . . 5
. . .  7 . 3  . . .
2 . 8  . . .  9 . 7
==
Solution
3 2 5  1 8 4  7 9 6
6 8 9  2 3 7  4 5 1
1 7 4  6 5 9  3 2 8

4 6 2  9 7 8  5 1 3
8 1 3  5 4 2  6 7 9
9 5 7  3 6 1  8 4 2

7 4 1  8 9 6  2 3 5
5 9 6  7 2 3  1 8 4
2 3 8  4 1 5  9 6 7
==
Create
Regexp::Sudoku:: -> new -> init
    ->      set_battenburg (qw [R2C2 R2C7 R7C2 R7C4 R7C5 R7C7])
    -> set_anti_battenburg (qw [R1C1 R1C8 R2C3 R2C6 R3C2 R3C7
                                R4C1 R5C8 R8C1 R8C8])
==
Name: Battenburg
Author: Clover
URL: https://www.youtube.com/watch?v=gZRw1oD5eck
Runtime: 00:02:35.2135
Lengths: 59470 (subject) & 26038 (pattern)
Number of statements: 896
Number of backreferences: 1690