This is more painful than expected. When defined, PengMod contains a as a 'native name string' representing the parameter. When PengMod.a gets set, it overwrites that parameter.

Current solutions:

• Add a new variable containing a list of parameters - but this will use one extra variable for almost every function, which'll really hurt.
• Add a variable containing parameters as a string. This'll use one more variable in some cases, but will be much more efficient for multiple arguments. It means that bound variables still need some kind of hack though.
• Add a list of parameter names to the front of the code var. This will save variables in most cases, but might need some work. Bound variables needed too.
• Add \xff to the beginning of each function parameter... Huge hack though

At the moment prepending to the code variable seems best. It's a relatively large change though.

... but we can't prepend to the code variable because now we're directly linking to the native string if it exists (to allow functions to be executed straight out of flash).

So either we ditch that and make everything more efficient, we do the hack, or we add the list of parameters.

Oh well... Added \xff. Turns out to be the tidiest way of fixing this and the least likely to break anything