Here's a little something I noticed a couple of months ago, but have only just noted down. Singlish allows you to do something interesting with the verb "want", but only under certain circumstances. For those who are familiar with German or with the history of the English language, you will notice that what I am about to outline in Singlish is a parallel phenomenon to what happened in English. German "will" means English "want" (verb). Formerly, in English, "will" did use to mean "want", and you can see this sense of the word in "last will and testament", or "I will it so", or "where there's a will, there's a way." Now, of course, we primarily use "will" in English as a future auxiliary, to indicate that an action will be happening in the future.
This particular semantic drift most likely occurred because if you want something, it is in the future, not in the present. (As for why something similar didn't happen in German: language change is explainable but not predictable.)
I confess, the first time I was given this explanation, part of me refused to accept it. Of course my brain understood why it was likely, but the fact that "will" is already grammaticalised as a future auxiliary blinded me to the process - I could not conceive of making that leap from "will" as in "want" to "will" as in future tense. I took the explanation at face value but didn't like it.
So imagine how intrigued I was when, while working on my spring-semester documentary, this gem of a Singlish sentence showed up in the musical I was following:
"I eat until I want to bao zha (explode) already!"
Any Singlish speaker will recognise this as a valid construction. "Want" here, however, does not indicate volition. You cannot substitute "would like" in the sentence: "I would like to explode." Neither can you substitute "will": "I eat until I will explode." The only acceptable substitution is the "going to" future: "I eat until I [am] going to explode already."
(N.B.: Singlish speakers with a linguistics background will notice that this entire sentence actually refers to a past event, without any explicit tense markers. The important thing, as you will no doubt also notice, is that the dependent clause occurs at a future time relative to the main clause.)
(E.T.A.: Upon a second reading, that's not the case, the sentence can also refer to the present time. Either way, it doesn't actually matter.)
The first explanation is that Singlish acquired this construction from Chinese, and you can see it in a direct translation:
"I eat until I want to explode already!" 我吃到我要爆炸了！
The question, then, is whether Chinese uses this construction to mark the future. The answer is: it does. Sort of.
As with many things in Chinese, the exact meaning is context-dependent, but take me at my word for now:
我要上学了。 Lit: I want to go to school already. Meaning: I'm going to go to school now.
我们要吃饭了。 Lit: We want to eat already. Meaning: We are going to eat now.
他们要走了。 Lit: They want to go already. Meaning: They are going to go now.
Other meanings are possible, but I don't want to get too much into the complexities here. The important thing is, in all three cases, a Singlish speaker can hear the literal translation and accept the dynamic translation as meaning the same thing.
Without actually conducting full-scale research on this, my guess is that it is the "already" inchoative aspect marker that does the trick - when used together with "already", "want" is focused from a generalised volition down to a specific, immediate-future time frame. Take away the "already" or the 了, and suddenly volition becomes the preferred interpretation in almost any context:
我要上学。 Lit: I want to go to school. Meaning: I want to go to school.
我们要吃饭。 Lit: We want to eat. Meaning: We want to eat.
他们要走。 Lit: They want to go. Meaning: They want to go.
Curiously, not all verbs can be used in all meanings with this construction. Not to be deliberately crude or morbid, but I think Singlish speakers will recognise these:
"I work until I want to die already." "I want to vomit blood already."
The volition interpretation is not possible in the above sentences, in the same way it is not possible to willingly want or choose to explode.
The thing is, of course, when the verb has a neutral or positive connotation it is much easier to assume that volition is intended. For example, you would have no issues with the usual English definition of "want" in these sentences:
"I want to sleep already." "I tired until I want to sleep already."
In fact, in the second sentence above, it is not possible to substitute "want" with the "going to" future. Volition is pretty much the only interpretation that makes sense.
The answer to untangling this construction lies somewhere in Chinese grammar. That's as far as I've worked it out in my head.