When I was studying participle phrases, I came across a sentence on a grammar teaching website, which I find trustful.The sentence is :
Opening the envelope, I found two concert tickets.
And the writer says in the explanation of this sentence that "A present participle clause can express an action that happens just before another action" and rewrites it as "I opened the envelope and I found two concert tickets."
But again on the same page, the writer says "If we want to make it clear that an action happens before another one, we use a perfect participle for the earlier action"
So why did the writer prefer to use a present participle clause instead of a perfect participle.In this example, is it obvious that we already assume that we cannot see what there is in the envelope before we opened it?Is it about context? or is it about the word just here?
If I say:
Having opened the envelope, I found two concert tickets.
Does the second sentence much more time passed between the opening and finding processes than the first sentence.
What is the difference between them in terms of meaning?