French past infinitive
The French past infinitive (l'infinitif passé) indicates an action that happened before another action (usually before the action of the main verb), but only when the subject of both verbs is the same.
In English, the past infinitive can sound awkward and we therefore often use a different verb form or reword the sentence completely. For example:
Je veux avoir terminé avant six heures.
I want to have finished by six o'clock. > I want to finish by six o'clock.
Elle regrette d'être partie trop tôt.
She regrets having left too early. > She regrets leaving too early.
Not that verbs conjugated into the infinitif passé require the same auxiliary verb that they need in other compound tenses, such as le passé composé.