[{"name":"john","comment":"alpha; alpha lima alpha bravo golf"},/**#this should match*/{"name":"fonz","comment":"foxtrot alpha bravo fonz; zulu"},/**#this shouldn't match*/{"name":"zoltan","comment":"golf alpha bravo zoltan; alpha bravo delta; lambda alpha"}/**#this should match due to alpha bravo delta*/]

db.collection.aggregate([{"$match":{"$expr":{"$regexMatch":{"input":"$comment","regex":{"$concat":["alpha bravo (?!","$name",")"]}}}}}])