Mind you I will leave the etymology out of it as much as possible.
Ρε, or Βρε come from ancient Greek (μωρέ) . They started their "carreer" as insults, meaning stupid, brainless.
Nowadays they are seldomly used as insult although "PE" in particular can vary from a mild-to-serious to light offense. However, it has lost the meaning of "brainless" and it is more or less an insult on its own right when used that way.
Example (in English with Re added)
A: Right! Are you going to listen to him
did you say re
Its most common use is as a sort of an interjection showing that two people are in very friendly terms. Most of the times, both "re" and "vre" are used when someone
a) wants to ask the other one for a favour
b) is frustrated with the other one
c) wants to show surprise
Re Tom will you close the light on your way out? I'm too tired to get up
Re Tom do lower the volume will you? I can't hear myself thinking
Wow! You did it all by yourself re Tom?