#   3 or more backticks
    (?![^`]*`) #   not followed by any more backticks on the same line
  |            # or
    (~){3,}    #   3 or more tildas
    (?![^~]*~) #   not followed by any more tildas on the same line
  )
  \s*          # allow for whitespace between code block start and info string
)0