in reply to Sudoku solver
Its because you used an obfuscation golf as a starting point :) an obfuscation that uses recursion based on global variables , not arguments passed -- the main purpose behind obfuscations is to hide(trick) how the code works, and purpose behind golf is to do it in as few characters as possible
If you want to do multiple games, you should use something from cpan ( sudoku solver ) like Games::Sudoku::Solver - Solve 9x9-Sudokus recursively
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