an event linked to a later event  - We felt we'd accomplished something quite important., an event finished by a certain time - Next week I'll have been here for three months., something that happened in the past, bu the exact time isn't known or isn't relevant to the discussion. - I've run a marathon. , event in the past but has a result or effect in the present - Oh no! I've lost my passport. , something that happened during a period that includes past and present - I've always run, but just for myself. / I've been living with a small tribe. /I've been doing volunteer work., very recent past - I've just heard the news., prediction about present or future - Don't call the house, she'll have left for work by now., perfect infinitive - It's great to have finished my exams., perfect gerund - I regret not having been here before.,

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