You're missing that Sun has three different Java platforms (J2SE, J2EE, and J2ME) that support different features and supports them on only a handful of operating systems (Windows and Solaris the best, Linux sort of second-hand, and everything else further down the line).

For example, I run Linux PPC. When will I see J2SE 1.5? It's worse if I run FreeBSD x86. For anything more "exotic", forget it.

Now consider where Perl 5 runs.