Perfect Modals and Past Perfect Tenses

may/might have + past participle: Indicates uncertainty about a past event. Use this when not sure if something occurred (e.g., Thierry might have played football for Everton FC).
should have + past participle: Used to show an expected event did not happen or to criticize past behavior (e.g., I should have offered to help my sister).
could have + past participle: Expresses uncertainty about the past or describes a past possibility that did not actually happen (e.g., Francis could have been a professional tennis player, but she injured her back).
can't/couldn't have + past participle: Shows certainty that a past event is not true (e.g., He can't have won the competition because he didn't enter it).
must have + past participle: Shows certainty that a past event is true (e.g., Working as a pilot must have been exciting).
would have + past participle: Indicates willingness to have done something that was not performed.
needn't have + past participle: Used for actions that were performed but were not necessary (e.g., I needn't have prepared for the meeting as it was cancelled).

Usage: Describes an action or situation finished before another past action, situation, or time. For example, by the time they arrived, the film had almost finished.
Structure: Formed using had (affirmative) or hadnot / hadn't (negative) followed by the past participle.
Time Expressions: Often paired with already, for, for a long time, ages, just, never, once, so far, yet, and specific dates like since 2007/June or since 2010 (e.g., We hadn't visited the Greek islands since 2010).

Usage:
- For actions that started in the past and were still in progress when another action began.
- For actions continuing over a period of time that affected a later action (e.g., She'd been training for six months, so was confident).
Structure: Formed using had been + -ing (e.g., Joel had been designing computer programs for years).
Common Phrases: Uses all day/night/week, for years, since, and How long...? in questions.

Formation: Question tags use a modal or auxiliary verb matching the main sentence. Affirmative sentences typically require a negative tag, while negative sentences require an affirmative tag.
Simple Tenses: Use do/does/did or don't/doesn't/didn't for the present or past simple.
Specific Irregular Tags:
- I'm early for the meeting, aren't I?
- Everyone is excited, aren't they?
- Let's go to the cinema, shall we?
- Don't touch the oven, will you?
- Remember to call me, will you/won't you?
- Be careful, won't you?
- This/That is so difficult, isn't it?
- These/Those are your keys, aren't they?