CPAN authors should look at the smoke tests for their modules to ensure that they're passing on Perl 5.18. The hash randomization change (and a few others) has bitten many a module that may currently be relying on undefined hash behavior. If you haven't checked your modules recently, you may be in for a surprise.

The problem is significant, especially when compounded by the fact that a single misbehaving module can block many more modules that may depend on it.

As an example (not to finger-point, but just to illustrate): Crypt::DES, Crypt::IDEA, Crypt::Blowfish, and…