Very good question. There's a grain of truth in what user947 said, even if s/he's wrong about tense and aspect.
Hebrew doesn't have a perfect tense: it has a qatal construction. Hebrew doesn't have an imperfect tense: it has a yiqtol construction. The terms of European grammar have enjoyed a long tradition as the default lens through which all other languages are analyzed, but now we're more open to the idea that they don't always fit.1
Of course, there's certainly overlap, which is what makes translation and intelligibility possible at all. But it's a mistake to think that there's a perfect match (no pun intended). Instead, we have to establish the range of semantic and syntactic information that words and grammatical forms convey through careful study of how they're used in different contexts.
How do we know what a word means or what SRE information a verb form indicates? By finding passages that appear unambiguous. And if they conflict — well, we assume there's a range of uses or change over time.
In the case of the qatal, there are contexts where it's certainly something that happened in the past. Interestingly, this is common in dialogue, compared to narration, where the wayyiqtol is preferred. But there are also contexts where it seems impossible to read it as a past event. One of the long-recognized ones is the so-called "prophetic perfect". If a prophet refers to future events using the qatal, what are we to make of it?2
Here's a good website that lists some of the functions of the qatal as catalogued by looking at different verses and figuring out the most likely meanings — over the couple thousand years people have been studying Hebrew grammar. These functions include completed actions in past time, yes; but also imaginary actions, performative actions, and stative actions. Those and others can be read into the poetry of the psalmists and prophets more easily than they can into historical narrative. I suggest reading over that page and seeing which ones seem to apply best in the verses you were asking about. (And if none of them do, keep asking questions!)
1 Nevertheless, the terms have stuck around.
2 Besides challenging much deeper-seated assumptions about prophecy. ;)