I ran your script and got the exact same results. I actually think that your script is quite good. Why? To quote the modules author, Paul Johnson:

"Branch and condition coverage data should be mostly accurate too, although not always what one might initially expect."

So, if you take your script and compare it with the results of other CPAN modules, the data produced by your script is very interesting. Paul Johnson ran Devel::Cover on some CPAN modules. The results might surprise you. See:

CPAN Coverage Report

He also wrote a paper on testing and code coverage:

Testing and Code Coverage

He also wrote a slide presentation to accompany the paper:

Testing and Code Coverage-Slides