I think Louis and Svend are confused about what mi() does and what arguments
it expects. Since the help file says it takes a list of arguments, I think
that if you type mi(var1-var6) it evaluates that as one argument that is
calulated as the difference between two variables. If a command does not
say it takes a varlist, then var1-var6 is not interpeted as a varlist, but a
valid math expression.
