def is_launch?(msg, exp_class)

      if exp_class != Ruote::Exp::DefineExpression
        false
      elsif %w[ launch regenerate ].include?(msg['action'])
        true
      else
        (msg['trigger'] == 'on_re_apply')
          # let re-apply "define" blocks, as in Ruote.define {}
      end
    end
def is_launch?(msg, exp_class)

      if exp_class != Ruote::Exp::DefineExpression
        false
      elsif %w[ launch regenerate ].include?(msg['action'])
        true
      else
        (msg['trigger'] == 'on_re_apply')
          # let re-apply "define" blocks, as in Ruote.define {}
      end
    end
Returns true if the msg is a "launch" (ie not a simply "apply").