What about dangerous syntactic elements?
The "variable variable" ($$var) will find a variable in the current scope by the name of $var. If used wrong, the remote user can modify or read any variable in the current scope. Basically a weaker eval.
Ex: you write some code $$uservar = 1;, then the remote user sets $uservar to "admin", causing $admin to be set to 1 in the current scope.
