Learn English – The present perfect with “once”: “I’ll do it once I have (had) a chance”

I do wonder sometimes at the 'rules' that people get taught for when to use what tense in English. They usually seem to work well for the examples used in teaching, but lead you down a misleading path as you get further into the language.

The perfect aspect, found in the present, past and future aspects, represents actions at are complete at the time of the sentence (past, present or future). It also puts a focus on the results of the action. The progressive aspect is about actions that are ongoing at the time of the sentence. The simple aspect, when the tense is neither perfect nor progressive, expresses fact - either about a specific action or a general or habitual truth.

When you say "I've received a message" you are saying that you have fully received it - you aren't in the process of receiving it - and putting focus on the result, the fact you have the message. In the same situation, you could also say "I received a message", which is a statement of fact without focus on the result, and is the past simple form. You might be meaning to focus on the fact of receiving, rather than on having the message.

Neither tense indicates any 'strength' of result. Neither indicates whether there is a result still ongoing or effective at the time of the sentence. It just focuses the result. There can also be differences of nuance between past simple and present perfect, but that can depend a great deal on the verb in question, and the subject. For example:

I knew the way from home to school.

This says that, at that time, you knew the way - it doesn't suggest you know it now, nor that you don't.

I knew love, once.

This suggests that you no longer know love.

I have known love.

This suggests that at some point you knew love, and may or may not know it now.

What tense to use is a much simpler, and yet more complex matter than a lot of teaching suggests.