He finally perceived where he had gone wrong.

perceived 是动词 perceive 的过去式。perceive 由前缀 per-（表示"完全"）和词根 -ceive（来自拉丁语 capere，意为"抓住、理解"）组成，意思是"察觉、认识到"。在这里指"意识到、认识到"自己的错误。