Null - language feature

Example from Jule:

nil

Example from Aardvark:

`null`

Example from Speedie:

|| msg = message()
while
 if msg != nil
  "msg exists"
   else
  "empty"
  return
 msg = nil

Example from Ion:

null

Languages with Null include C3, Jule, Aardvark, Speedie, Ion