Attempt to modify read-only data

[William Barry <barryw@ucs.orst.edu>]

I am having trouble with the following test file using 
the 10-26-94 version of clisp under Linux 
-----test2.lisp-----------------
(in-package 'user)
(defvar temp-string "Matson, I need you")
(setf (char temp-string 0) #\W)
(print temp-string)
---------------------------------------------
I get the following output

> (load 'test2.lisp)
;; Loading file test2.lisp ...
*** - Attempt to modify read-only data
1. Break> up

EVAL frame for form (SETF (CHAR TEMP-STRING 0) #\W)
1. Break>
---------------------------------------------------
It works fine using the dos version of clisp.
Can anyone suggest a way of fixing this?
Thanks,
Bill Barry