# Perfect vs non-perfect

1. She wants to finish it when you return
2. She wants to have finished it when you return.

These are examples from my text book. It says they are different in meaning.

I made 3 and 4. I think they mean the same, am I correct?

1. She wants to finish it by the time you return.
2. She wants to have finished it by the time you return.
• Nope: 1> she wants to finish it when that person arrives, not by that time. (I am not a native though). May 8, 2023 at 1:19
• @Cardinal Maybe I didn't make myself clear; what I wanted to ask was whether 3 and 4 mean the same thing May 8, 2023 at 1:24

"She wants to finish it when you return"

This means first you will return, and at that time she'll finish it.

"She wants to have finished it when you return"

This means she wants to finish it before you return.

Sentences (2), (3) and (4) mean the same thing.

More detail:
When we have a sentence where "when" conjoins two action verbs with the same tense, it means the subordinate verb triggers the main verb, in other words, the subordinate verb (the verb with "when") always happens first and causes the main verb to happen. In these sentences, you can replace "when" with "after" to understand the time order:

She wants to finish it after you return.

But in a sentence where the tenses are different, the tenses themselves determine which action happens first. Present perfect refers to the past, so it happens before the simple present verb. In your example sentences (2), (3) and (4), this means "finish" happens before "return".

The OP is correct.

1: She wants to finish it when you return
means she will start the process of "finishing" upon your return
2: She wants to have finished it when you return
means she will already have finished by then

3: She wants to finish it by the time you return
4: She wants to have finished it by the time you return

Both 3 and 4 mean the same as 2.

Your textbook is correct that sentences 1 and 2 have different meanings.

To make the example more concrete, imagine 'it' refers to 'assembling the bookshelf'. Then, "She wants to finish it when you return" means that the action of finishing assembling the bookshelf is meant to happen at or after that of you returning. This would imply she's waiting for you to return before finishing assembling the bookshelf.

"She wants to have finished it when you return" means that she wants to be done assembling the bookshelf by the time you get back. The action of assembling the bookshelf happens before that of you returning.

The relative sequence of the two actions is reversed between sentences 1 and 2.

So, for your examples 3 and 4, 4 definitely has the same meaning as the original sentence 2. I'm not sure that your sentence 3 is grammatically correct, but it sounds perfectly acceptable for something someone might say in normal conversation. It would be a less formal/precise way of saying the same thing as in 4.

@Cardinal pointed out the important detail that changing 'when you return' to 'by the time you return' changes the time relationship of the two events.