There is no ebuild in portage for DBD::Sybase. I will attach an ebuild that I have based on DBD::mysql.
Created attachment 17499 [details] DBD::Sybase ebuild
The policy on perl modules in Gentoo is that they are only specifically included in the portage tree if they are a dependency of an app or they provide utilities. Unless I'm mistaken, this doesn't meet these requirements, and if that is the case, g-cpan.pl should be used for installation instead. Thanks for the submission anyway.