[plt-scheme] R5RS is totally useless for PLT, and I presume that R6RS is, also.

PLT Scheme 4.1 has totally scuttled my project, which was started
under PLT version 360, in which R5RS programs could interact freely
with PLT Scheme code, and PLT code could be (and was) written as if
it was R5RS with a few extensions.

Today, I discovered that my ISP has upgraded to PLT 4.1.2, where they
have introduced a feature (among many) they claimed wouldn't affect
"most code:" Immutable lists. The HTML-parsing library my program uses
is heavily infused with set-car! and set-cdr!. All kinds of functions
are
dependent on it, and their callers are in turn dependent on the
mutating
behavior. In short, to get rid of list mutation, you'd have to rewrite
the entire library from scratch (PLT's html module sucks, BTW).

PLT Scheme still supports mutable lists, but they're a separate data
type, which means that I can't pass the lists that come out of the
HTML-parsing library to any function that uses any PLT Scheme library
call to work with lists.  All the code I wrote to accept the output of
this
library is suddenly completely useless.

While trying to come up with a workaround (a KLUDGE), I was delighted
to discover that PLT Scheme 4.1.2 doesn't support nested (define)
forms,
either.

Useless.