Execute detect block data tags

/execute @a ~ ~ ~ detect ~ ~-1 ~ dropper 3 /blockdata ~ ~-1 ~ {Items:[0:{id:dirt,Slot:4b}]}

/execute @a ~ ~ ~ detect ~ ~-1 ~ dropper 3 {Items:[0:{id:stone}]} /blockdata ~ ~-1 ~ {Items:[0:{id:dirt,Slot:4b}]}