The buses run from 4 a.m. to midnight 'at regular intervals'. [=there is the same amount of time between buses]
It's nothing special, just a 'regular' [='basic'] stereo. = It's just a 'regular old' stereo.
He is one of the store's 'regular customers'. [=customers who shop at the store frequently]
(..) - Oh, milk steak. Hmm? Hmm? What? - Milk steak. - I'm not putting milk steak. Just put steak. Just put regular steak. And then- I'm gonna put steak. Put milk steak. She'll know what it is. She won't know. Nobody knows what that is. She'll know what it is. (..)2009 TvShow: It's Always Sunny in Philadelphia Title: The Waitress Is Getting Married Season: 5 Episode 5