I would probably avoid using it except in oral language. People often erroneously think that English doesn't use tones like chinese does. It does, and it usually happens in interjections. A different tone of the interjection can express completely different meanings to the phrase. This is one example. Pronounced one way, it could mean 'Oh dear, here we go again...' - a type of resigned fate. Pronounced another way, it could mean 'What's going on here?' having a surprised and curious meaning. I use 'eh' (pronounced like the name of 'a') as an example of this. I can say the one word four different ways, and clearly express 4 different meanings to a native speaker...

from the TV series, How I Met Your Mother

Never heard it. Where is it used?