x <- c(
    "The dog and the man play in the park.",
    "The man plays with the dog.",
    "That is the man's hat.",
    "Man I love that dog!",
    "I'm dog tired"
)

## this works but I want a single regex
grepl("^(?=.*\\bman\\b)(?=.*\\bdog\\b)", x, ignore.case=TRUE, perl=TRUE)