Hi Sathya,
Perhaps "" also matches everything. What about trying "$^" or "ZZZZXCZAXCZXC"?
Additionally, if you are building with the make build system, you might want to verify that the relevant config value is being updated in .config. If you are building with the CMake build system, then the regex config setting is in a different location
and can be changed in the CMake cache.
Kind regards,
Kent McLeod