support $!x as lvalue
Merge commit '72f8b5a4264d0178a73a5fa65104d70877de83a2'
Block should generate PVIP_NODE_BLOCK for managing variable scope.
Merge commit '050223e02975dd201ddfb46f306a76f7e7a9c7b7'
oops. duplicated blocks.
Merge commit '7754356d130b125999b6014eba74d7206f1917c1'