When specifying a file path in TExpressive you have three options; an absolute path, a relative path and a relative-to-base path. The paths have the format:
Absolute and relative paths work the same as they do everywhere else under Windows. Note however that relative paths are relative to the file currently being processed. Relative-to-base paths work relative to the base path set. The base path to use is defined in the parameter "_BasePath"; setting this parameter to another value changes the base path. If you clear or unset this parameter then relative-to-base paths will be treated like normal relative paths (relative to the file being processed). Another way to set the base path is to specify the "/BasePath" command line argument.