If only I had gone by taxi.

我要是乘出租车去就好了。

《牛津词典》

'If only I had known you then,' he said wistfully.

“要是我那时认识你就好了。”他向往地说道。

《牛津词典》

If only I had done something!

我当时要是做点什么就好了！

youdao

If only I had chosen to become a doctor, instead of having chosen to become a lawyer.

要是我选择成为一名医生，而不是选择成为一名律师。

耶鲁公开课 - 死亡课程节选

If I had lists of lists of lists, then it would only take out the first level of it.

贴到另外一个数组的后面，它当然是实现了套数组的操作。

麻省理工公开课 - 计算机科学及编程导论课程节选

And then, you start thinking, "Well, I could really start doing this if only X and if I had this person or if this technology existed or if this happened or this happened."

之后，你会开始思考，恩，只要某项条件成熟了，只要我认识这个人,或是如果这个技术存在,或是如果这个或那个发生了，我就能开始落实这个点子了“

斯坦福公开课 - Twitter之父Jack.Dorsey演讲：好奇和灵感的力量课程节选

If only I had learned a trade before coming to the United States, like plumbing, or home renovation, or Qigong.

NEWYORKER: The House Behind a Weeping Cherry

If only I had bet on her winning, I might be able to buy a sailboat, or build a concert hall.

BBC: Musical destinations: Geneva, Switzerland

If only I had David Cameron's Lexus following respectfully behind.

BBC: NEWS | UK | Magazine | Cycle warriors