I suspect the problem is that you should be using perl -I lib (capital i), not perl -l lib (lower-case L).

What you want to do is tell Perl to add "lib" to the include path. What you've actually been doing is telling Perl to execute the script "lib" with magic newlines enabled. :)

As for why Perl's reaction to being asked to execute a directory is to do nothing silently and signal success, I have no idea.