[chromatic]

The testing stuff is good and it's the direction everyone should be going but not having it obviously isn't too much of a problem because so few systems currently have it....

The Perl 5 Porters mailing list has automated mailings which test CPAN against bleadperl to discover which, if any, commits break existing CPAN distributions. This helps p5p revert genuine mistakes and CPAN authors to patch their bugs.

I know that several minor revisions of other languages have broken several popular extension libraries.