As Sogliphy pointed out the match() function I provided gets the response data from the projector until it encounters a "\r" or it reaches the 2s (2000) timeout, which comes first. Your projector replays for each command it gets with a string that ends with "\r".

So the function above does this. Sends the projector the command and then:
a) waits for the projector to respond to the given command
b) waits for a response from the projector until the given time has passed.

So the answer to your question is:
match(":POWR1\r", "\r", 2000) ... sends the :POWR1\r" command and waits for the "\r" from the projector.