used to describe words produced without any mistakes, or a person who is able to repeat a particular text from memory without making any mistakes

His mother rehearsed his lines with him and by the time the play opened he was letter-perfect. 他妈妈跟他对台词，到演出开始时他已经背得滚瓜烂熟了。

"Your German was letter-perfect," Franz said. “你的德语讲得一字不错。”弗朗兹说道。

a letter-perfect rendition/recitation 娴熟的表演／一字不差的背诵