This issue is resolved. I realized that Nim uses platform-specific pattern matching for filenames. This depends on the OS in use.
In this case the Windows CLI has several quirks in the way it uses wildcards (*, ? etc.) for matching filenames. These quirks seem to have been inherited from the early DOS days. This would explain why I am not getting the expected results with my above code sample. You may read more about Windows filename pattern matching at: [https://blogs.msdn.microsoft.com/jeremykuhne/2017/06/04/wildcards-in-windows](https://blogs.msdn.microsoft.com/jeremykuhne/2017/06/04/wildcards-in-windows)/
