StringConstant actor will not accept strings with '$'
Try entering a string like 'foo$bar' in the StringConstant actor. It will give an error trying to evaluate 'bar' as a parameter. It looks like it is evaluating the string using Ptolemy's expression language.
I think this is because Kepler's StringActor is NOT the same as the Ptolemy StringActor. It has been modified to allow the string to be set to a filename and I think this causes an evaluation of the string. This may be useful for setting filenames, but it causes problems with some strings.