Most commonly used in the same context as "oh, damn". Used to express frustration, anxiety, depression, etc. Ocasionally the second syllable is prolonged to demonstrate any emotion in an extreme fashion.

an expression of annoyance, anxiety and minor anger.

How robots say goodbye according to the Alpha-Beta Bots on Sesame Street episode. You can find proof of this on muppet.wikia.com (Episode_4185).

also spelled "Blergh!"
Interjection to show utter disgust, short of vomiting.

n,v,adj

Anything bad or upsetting, something used when there is nothing else to say, and insult

computer code The second in a list of three terms. Similar to foo and bar, spam and eggs, you have blah, blerg, and blarf

to get FUCKED up