In the documentation (INSTALL) nothing of the update stands on 2.64. Is that the same means?
I don't understand this question, and I assume it got mangled in translation to english. Can you rephrase it?
If you're asking if the install procedure for 2.64 is the same as 2.63, yes it is.
What is to be considered still?
The only thing to consider, AFAIK, is why you are still running 2.63, which contains a known DoS vulnerability.
The only possible side issue I can think of is if you use the Mail::SpamAssassin::SpamCopURI add-on to provide SURBL support you'll have to download the latest version of that and install it again after installing SA 2.64.. This isn't too surprising since the SpamCopURI package actually patches part of the SA code.
You'll also need to remove the spamcop_uri.cf file from /etc/mail/spamassassin/ for 2.64's "make test" to pass. It doesn't have the SpamCopURI patch, and thus won't understand those rules.
Does 2.64 with perl 5.6.* work?
In general the differences between 2.63 and 2.64 are pretty minimal in terms of code. It should run anywhere 2.63 does, but I'll admit I've not tested this.
I'm quite sure part of the reason 2.64 was released is to provide one last version of SA that fixes the DoS for users of old versions of perl and can't migrate to 3.x.
SA 2.64 should still run on even 5.005, and that's what minimum version 2.64's SpamAssassin.pm calls for.
SA 3.0 will require 5.6.1 or higher, but even it will run on perl 5.6.* with the exclusion of 5.6.0.
