If I had V-ed, I would ...
  結構︰If…had+過去分詞…,主詞+would/should 等+原形動詞+now/today
  說明︰這是<時態>不一致時的假設<句型>,亦稱混合假設條件句。即:if <子句>若與過去事實相反,用<過去完成式>表示;而<主要子句>若與現在事實相反,則用過去式<助動詞>表示。此類<主要子句>句尾通常有表現在的<時間副詞>,如 now,today 等。
  If he had worked harder when young, he would be well off now.
  如果他年輕時多努力一點,現在就能過得舒服些。
  If I had been rich ten years ago, I could buy that house today.
  如果十年前我有錢,今天我就能買下那棟房子了。
  Had he told the truth, he wouldn’t be punished now.如果他當時肯說實話,現在就不會受罪了。
  Had he followed the doctor’s advice, he might be alive now.
  當時他要是聽了醫生的建議,現在可能還活著。

  I wish ... + V-ed ...
  結構︰I wish+(that)+主詞+動詞過去式/過去完成式(had+過去分詞)…
  說明︰I wish 之後以 that <子句>為<受詞>時,該<子句>的<動詞>一定要用<假設語氣>:若<動詞>用過去式,表示與現在事實相反的願望;若用<過去完成式>,則表示與過去事實相反的願望。“I wish+that-<子句>”的<句型>也可用“I would rather+that-<子句>”取代。而 I hope 之後以 that <子句>做<受詞>時,該<子句>用一般<時態>。
  I wish there were meadows and lambs. 但願有草地與小羊。
  I wish I were as tall as you. 但願我像你一樣高。
  I wish he could tell us. 但願他能告訴我們。
  I wish (=I would rather) he could come tomorrow. 但願他明天能來。
  I wish you had not been caught in the rain yesterday. 但願昨天你們沒有淋到雨。
  I wish you had not told the truth. 但願你沒有說實話。
  I wish I had known you ten years ago. 真希望十年前就已經認識你。

  If only + V-ed
  結構︰If only+過去式/過去完成式
  說明︰此句型意為“要是…就好了。”用過去式,表示與現在事實相反;若用<過去完成式>,則表示與過去事實相反。
  If only I had a rich father. 要是我有個有錢的爸爸就好了。
  If only he had been here. 要是他當時在這兒就好了。
  If only I had another chance. 要是我再有一次機會就好了。