My Impossible Plan to implement this Impossible Dream would be to take a subset of Perl5 that can be parsed statically and implement that. Basically what PHP should have been if it was run by people who knew what they were doing.
From there, you can integrate the new implementation into the CPAN testing system. Try to get the major module authors to commit to passing their releases under the new system.
"There is no shame in being self-taught, only in not trying to learn in the first place." -- Atrus, Myst: The Book of D'ni.