CodeGolf: Find Unique Value

.BagHash.invert.Hash{1}.say for [[ 1, 1, 1, 2, 1, 1 ],
     [ 3, 5, 5, 5, 5 ],
     [ 9, 2, 9, 9, 9, 9, 9 ],
     [ 4, 4, 4, 6 ],
     [ 5, 8, 8 ],
     [ 8, 5, 8 ],
     [ 8, 8, 5 ] ];