There's nothing preventing symbol table modifications done by Perl modules at compile time to be reified into some sort of linkage unit, with which a parser could then statically parse the code.
Similarly it's possible to prove that a certain block of code does nothing but link in such deterministic units, removing the nondeterminism of function prototypes.
Most of the source code out there can be parsed statically without resorting to anything drastic. The semantics of this hypothetical Perl 5 variant do differ, but as a strict subset it will still properly most of the useful code out there.
That's not the point. It is interesting, from a programming language theory perspective, that Perl 5 can not be parsed statically. The person who wrote the proof sketch cares very much about the practical implications of that theoretical result because he's writing Perl parsing libraries.
Also, what you're describing is no longer static parsing.
Similarly it's possible to prove that a certain block of code does nothing but link in such deterministic units, removing the nondeterminism of function prototypes.
Most of the source code out there can be parsed statically without resorting to anything drastic. The semantics of this hypothetical Perl 5 variant do differ, but as a strict subset it will still properly most of the useful code out there.