I didn’t know anything about “Poèmes Algol” before reading this post, this intrigues me 
I’m guessing, in Oulipo fashion, that it was an attempt at constructing poems using a very strict constraint, which is to only use the Algol base words. And I’m also guessing that, at the time, “computer talk” was seen as a new and interesting language, and Arnaud wanted to play with it, or something like that. By the way, Felix, I wouldn’t have guessed the connection between MACHINALGOL and the Algol language, good job for finding it 
On the topic of translating the Algol keywords, I think that his translation is actually “correct” - that is, in line with how French people write pseudocode, even nowadays: in particular, we use infinitive forms when English uses what looks like imperative. And I don’t even think it’s just a bad translation someone did one day and everyone stuck with it for some reason: I’m pretty sure cookbooks in French use the infinitive to detail the steps (as in “Battre les oeufs en neige” or “Faire cuire à 175°C”). And French intro classes to algorithmics will tell you that an algorithm is like a cooking recipe
Interestingly, this also carries to interactive fiction: French players have a tendency to use infinitive forms of verbs (imperative is also supported), when English players seem to think of it as imperative. We talked a little bit about it in the last FrenchComp’s thread.
If I may discuss the translations (and those poems are pretty hard to translate, even to a native speaker!!), the first one seems very complicated to me because of the multiple meanings every word has: “chaîne” means string, but also chain or channel; “tableau” means array but also painting, and “valeur” means value but also worth. Thus it is impossible to translate in English using only ALGOL words, and merely very hard if you lift that restriction.
I might have found some meaning (although I’m sure it’s the wrong one), so I’ll have a go at it:
This would be the clearer, more expansive interpretation that I have in mind:
(very, very loose interpretation!)
As for the fourth one, it’s actually rather unsubtle:
The sausage referring of course to… yknow.