Try it out at http://perlcritic.com/. The feedback is usable - when the tool finds something to complain about, it provides a link to documentation explaining what it didn't like, and the way it "should be".

I used Perl::Critic a few years ago on a contract to demonstrate the code I had written was over 90% "Perl-Critic" compliant.

For the few non compliant programs I then documented why and what could be done next (in nearly all cases these programs hadn't been refactored yet).

The client was extremely pleased. So much so he asked me to perform a program audit on the complete Perl codebase he had ;-)

Has someone done something similar with other languages?