Ruby works great for this, but is unfortuantely not installed on many systems -- but this isn't just bad luck, I think it's a consequence of the fact that ruby code written two years ago has a pretty good chance of not running on the recent version; and code written for the recent version without thinking about backwards compat also has a good chance of not running on ruby of two years ago...

Means as a language it's not suitable for "have it installed on every system and then just throw code at it that will work, and keep working" like Perl. Even if you could convince all the distro maintainers to include it, you'd never have the version you want/need. Which would be different for different scripts, and you'd have to be constantly updating all your routine maintenance scripts you just wanted to put there and have them keep working -- which with Perl you could.

I wish ruby were more about backwards and forwards compat, but it isn't.

I don't think I have ruby on any system I administer, but perl is almost always there.