When teaching grammar, and in particular passive verb groups, I’ve often found it useful to use the Singlish passive marker, kena — this is because many students have great difficulty telling whether a clause is in the active or passive voice.
In English, the passive voice is usually formed with the appropriate form of be or get:
(1) Shirley was/got promoted last week.
(2) Shirley was/got cheated last week.
Using the passive marker kena is a useful test for the passive voice: if it can be used in place of be/get, then the clause is probably passive. However, the ‘kena’ test has an important limitation: it can be used only with outcomes considered to be negative or undesired:
(3) * Shirley kena promoted last week. (positive outcome, ungrammatical in Singlish)
(4) Shirley kena cheated last week. (negative outcome, grammatical in Singlish)
Leaving aside the issue of preferred verb forms in Singlish (kena cheat is more likely), we note that (4) is good because it describes an event considered negative or undesired (i.e. nobody likes to be cheated), but (3) is definitely out because most people would wish to be promoted. For this reason, kena is said to a marker of the adversative passive.