Disallow conflicting use of variables named "password" and "names". If such
  a variable is declared, and "SET ... = ..." is used for them, an error is
  returned; the user must resolve the conflict by either using `var` (indicating
  that the local variable is set) or by renaming the variable.
  This is necessary since setting "password" and "names" are treated as special
  cases by the parser.