x <- c("123AB123 Electrical CDe FG123-4 ...",
"12/1/17 ABCD How are you today A123B",
"20.9.12 Eat / Drink XY1234 for PQRS1",
"Going home H123a1 ab-cd1",
"Change channel for al1234 to al5678")
res2 <- regmatches(x, gregexpr("(?<!\\S)(?:(?=\\S*\\p{L})(?=\\S*\\d)\\S+|(?:\\S*\\p{Lu}){2}\\S*)", x, perl=TRUE))
unlist(lapply(res2, function(c) paste(unlist(c), collapse=" ")))
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