It looks like there is a bug in how parameter substitution is handled in PreprocessorContext.java that causes parameter values that contain backslashed to not be processed correctly, resulting in the backslashes being lost. For example, if you had the following:
You would expect the echo command to produce the output $foo\bar but the actual value that gets substituted is \$foobar. This is happening because the substitute method in PreprocessorContext.java uses a regular expression replacement instead of a basic string substitution and $ and \ are special characters. The code attempts to escape $, but does not escape backslash.