There are many languages that have "eval" and yet have unambiguous parse trees for the actual code of the program (as opposed to the code evaluated at runtime).
If you run this Python program you'll see it prints out a complete parse tree of the program BEFORE it runs eval. Before you jump down my throat, I'm not saying that this makes Python a better language than Perl. It's just a fact that a language can be constructed so that "eval" is totally handled at runtime and does not affect the parsability of the program.
x = eval(sys.stdin.readline())
print "yes", x
print "no", x
He is saying that in order to statically parse an eval block, you must know when_it_halts - or in otherwords - what it does; this is impossible with out actually running the eval block, and is clearly related to the halting problem.