I don't think I have ever had perltidy() break my code in the four or five year I have been using it. I have seen it flush out syntactical faux-pas on my part; but I have not had it generate broken code, unless the code was already broken to begin with. That said, I always run what ever test-suite I have available against both the original code and the perltidy'd code and then explain all of the diffs before I rename/commit/production-ize the .tdy file. Just another Old Paranoid Programmer, I suppose.
I Go Back to Sleep, Now.