The CPAN link (which is the 5.25 version distributed with perl 5.10) is older, at least according to the version number/date than the v6.2 one in the "official" distribution @ Ilya's site

The other versions mentioned in emacswiki are probably based on/synched with the 6.2 version mentioned above, and may have some updates that ilya's version doesn't have, like more 5.10 syntax support.

In any case you will get a cperl-mode distributed with both emacs and perl, and if you use fairly recent versions of either you should get at least one usable version of cperl-mode. If you want to get the best mode you can get, you should probably start with ilya's site and then explore the other links on emacswiki to see what version suits you most.

As for me, I'm mostly writing perl 5.8 compatible code at the moment and Ilya's 6.2 version works fine for that.