The key to exercise solutions in chapter 8.2 - Grammar for the textbook Focus 4 (2nd edition) - Student's Book with authors Sue Kay, Vaughan Jones and Daniel Brawshaw from Pearson Education
Question
Look at the example phrases in Exercise 6 and choose the correct tense in the rule in GRAMMAR FOCUS II.
Answer
You use wish / if only + sb + Past Perfect to talk about past regrets.