How to save a CAS program

[Alberto Candel]

As I noted in this post http://www.hpmuseum.org/forum/thread-1864.html the Prime will rewrite CAS program to its own taste. In a program similar to the one in that post (CASE to PIECEWISE), I used the Sto key instad of the := combination for initializing some local variables. The Prime then replaced some of those Sto with an equal = sign (intead of the := combination). Running that program it reports "unitialized variable" when encountering = intead of :=. I tried to edit the = to :=, but since the program does not pass the Check test, it will to record any edits and ... forever.

So, does anybody know how to actually make these edits to CAS programs recorded? Thank you!