Scope of local parameters

["Haakon Riiser" <haakon.riiser@xxxxxxxxxx>]

Are there ways to limit the scope of local parameters besides
functions?  Say you want to colorize the prompt, and you use
helper variables for the color escape sequences:

  local RED=...
  local GREEN=...
  local BLUE=...

  PS1=<use RGB variables here>

If I do this in ~/.zshrc, or a file sourced by .zshrc, the
variables declared local do not disappear after sourcing ~/.zshrc.

One way to work around this is to wrap the PS1 initialization in
an auxiliary function, but then you have the same problem with
the scope of the function. :-)  Alternatively, one could

  unset RED GREEN BLUE

after setting PS1, but this doesn't feel quite right.  What if
the parameters RED GREEN BLUE already existed?  There has to be
a better way.

-- 
 Haakon