/effect doesn't recognize @a/r/p

So I am building a map and in spawn chunks I have a clock running. This clock has a command block hooked up to it saying /effect @a 23 1 10. (effect everyone with saturation 10 for one second is basically what that means) But, it didn't do anything after I was hungry, so I copied the text and pasted it into chat and it said that it couldn't recognize anyone called @a. I tested this with other effects too, and it still didn't work.

Also, I was playing on a bukkit server with worldedit and superpotions, if that matters.