The Perpetual Check can save you half a point when your chess position is bad and you are losing. There might be a chance to force an eternal check.
If your position is ruined because you played badly or had a bad day, then there is no other way to save the game. In the following positions the opponent has more material (pieces) and is going to win or you will get checkmated soon. Your only chance is to force a draw with repeated checks.
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