In Debian, you can pull packages from multiple sources, so you might¹ be able to get your base OS from 'stable' and pull certain packages from 'testing' or 'unstable'. See http://www.argon.org/~roderick/apt-pinning.html for information on setting this up.

Rather than using testing or unstable, you might be able to find some of the packages you need at http://www.backports.org. Not Perl, though, but they do have Apache2.

A nice middle ground between building everything from upstream sources, or suffering through outdated packages might be to build your own .deb packages of perl 5.8.x and its dependancies. I haven't tried this for something as complex as Perl or Apache, but for many other packages it's a simple matter of downloading the source packages from 'unstable' and rebuilding them on 'stable'.

1 - I say "might", because doing so might require upgrading the dependancies of Perl and Apache to the versions from 'testing', at which point you're basically better off just switching the entire thing rather than trying to track a 'stable' base and 'testing' for your apps.