"The applications you write today in Perl 5 will still be capable of running in Perl 5 in a decade. A minor update here and there may be necessary, but they will still be runnable."

Sure, but I'm an Open Source guy. I want other people than me to run my software too ... and this might be hard at some point. Technically, every program ever written is still runnable, but the effort might increase over the years.

This is a straw man argument. I don't see Anonymous Monk suggesting that nobody would be maintaining your project in ten years. Any piece of software that is around and being used in ten years will have had updates by some maintainer along the way.

The other fallacy in this reasoning is that it seems to assume applications written in other languages won't need to follow similar maintenance paths. I assure you that if you write an application today in any live programming language, if it's still in broad use ten years from today, it will have had updates somewhere along the way.

Most code cleanly written in Perl 5 ten years ago would require no changes to run in Perl 5 now. There are a few exceptions for code that used pseudo-hashes, or $*, among a few other things. And unclean code that was depending on hash ordering would fail, but that was documented ten years ago to be a bad practice.

That is actually a better situation than code written ten years ago in many other languages. Perl 5 has done a better job of maintaining backwards compatibility than most other actively developed languages. And I see no reason to believe that trend wouldn't continue into the future.

If you don't want to come back to Perl 5, don't. But it would be silly to eschew Perl 5 out of fear of events that nobody can predict. If it is a good language for getting things done right now, use it. It's not like you're going to be able to count on Ruby being included with Linux in ten years, or five, or 1. Perl, yes for 1, and five, and probably for ten.