Your rule ("don't change anything") is also an argument for never adding features! There's a tradeoff here that you're glossing over. Given that each newer ver

Your rule ("don't change anything") is also an argument for never adding features! There's a tradeoff here that you're glossing over. Given that each newer version is presumably some amount better than the previous one, eventually the benefits of upgrading will outweigh the costs, at least if you're going to continue making changes to your software. I don't think chromatic was saying "everyone should immediately upgrade to the latest version of Perl". I think he was saying "upgrading to the latest version of Perl isn't as scary/costly as some people think; I did it, and here's my experience." Also, keep in mind that sometimes there are hidden bugs in the old version, too. My employer just ran into a problem with the de-allocation of deeply nested structures being implemented inefficiently in Perl 5.8 (which has been in production for close to a decade); the bug was fixed in 5.14.