How many major versions of Perl do you know about?
What is the distribution of these different versions of Perl across various OSes and OS versions?
Hint: Lots of backward-incompatible changes tend to get made around different major versions. Having Perl 4 is not like having Perl 5 which is not like Perl 6.
If you want to claim broad compatibility, you can't just look at the latest distributions. You have to look at OSes other than Linux. You have to look at older versions of OSes, too. And don't forget the billions of embedded and handheld devices, too.