I'm not sure what you mean, do you change those in the Arc source code? I'm sort of new to all of this, just downloaded arc2 a few days ago and got this error in mzscheme on my Mac and FreeBSD box:
compile: bad syntax; function application is not allowed, because no #%app syntax transformer is bound in: (quote nil)
=== context ===
~/arc2/ac.scm:960:0: aload1
That's what my post intends to "fix", assuming that this is a problem for other people. (Fix is quoted because I don't know what functionality this would break)
The very latest mzschemes—those even more recent than 372—have switched to immutable lists instead of mutable ones; i.e. (set-car! my-lst) and the like no longer work. However, you can get mutable lists with the mcons, mcar, and mcdr operators, and this is what sacado was referring to.