If I set mode to 'Replace' & 'Entire filename', it is expected the input regexp should match the entire filename, but in fact, the regexp only matches part of the filename if it contains some dots.
Just create a file named 123.abc, input the regexp .* and replace with @, the expected filename should be @.
But this buggy software just give totally wired result. And you'll easily find even more bugs if you continue to use it.
Have you even tested your program?