def create_method_from_expressions
      expr = expressions.map {|e| "(#{parse_expression(e)})" }.join(" && ")

      instance_eval(<<-eof, __FILE__, __LINE__ + 1)
        begin; undef __execute; rescue NameError; end
        def __execute; #{expr}; end
      eof
    end
def create_method_from_expressions
      expr = expressions.map {|e| "(#{parse_expression(e)})" }.join(" && ")

      instance_eval(<<-eof, __FILE__, __LINE__ + 1)
        begin; undef __execute; rescue NameError; end
        def __execute; #{expr}; end
      eof
    end
Creates the +__execute+ method by evaluating the expressions
 as Ruby code
 @return [void]