Task: Program Execution
Input (English): 7, 1, x, 2, E, 7, 9
Output (English): [['7', '1', 'x', '2', 'E', '7'], ['7', '1', 'x', '2', 'E', '9'], ['7', '1', 'x', '2', '7', '9'], ['7', '1', 'x', 'E', '7', '9'], ['7', '1', '2', 'E', '7', '9'], ['7', 'x', '2', 'E', '7', '9'], ['1', 'x', '2', 'E', '7', '9']]