Useful tools for finding syntactic and semantic errors in the input files are provided by the menu Debug in the Main-Window (in fact it is almost impossible to find errors in bigger files without them).
With the entry Debug/Log to File you can redirect debugging messages into the log file vdog.log. The entry Debug/Show Log opens a window, which displays the contents of the log file (updates automatically when the log file changes). With the menu Debug/Clear Log you can clear the contents of the log file and the log window.
By increasing the log level via the menu entry Debug/Log Level you can get more information about the location of errors in the input files. If you for example increase the log level to 3, and remove a comma in the example file from above, you get the output shown in Figure 2.5.