anchor.diff:  
   eval_std_test() ->
       Script = "{seq, {numvar, \"V1\"}, {round_robin, [10,11]}}.",
  -    Meta = [{worker_id, 4}],
  +    Meta = [{worker_id, 4}, {pool_id, 1}],
       Env = [{"V1", "5"}],
       AST = mzbl_ast:add_meta(mzbl_script:parse(Script), Meta),
       R = mzbl_interpreter:eval_std(AST, Env),
  
positive.code: 
  round_robin_test_() ->
      Script = "[{test_method, {round_robin, [\"1\", \"2\", \"3\"]}}].",
      [?_assertEqual("1", catch run(Script, [{worker_id, 1}])),
       ?_assertEqual("2", catch run(Script, [{worker_id, 2}])),
       ?_assertEqual("1", catch run(Script, [{worker_id, 301}]))].
  
  sequence_test() ->
      Script = "[{test_method, {sprintf, \"~p\", [{seq, 1, 7}]}}].",
  
negative.code: 
  eval_std_compiled_test() ->
      Script = "{seq, {numvar, \"V1\"}, {round_robin, [10,11]}}.",
      Meta = [{worker_id, 4}, {pool_id, 1}],
      Env = [{"V1", "5"}],
      AST = mzbl_ast:add_meta(mzbl_script:parse(Script), Meta),
      NewAST = compile_and_load(AST, Env),
  