A <- c("Hello world", "Green 44", "Hot Beer", "Bip 6t")
sub("([[:alpha:]]+)", "*\\1*", A)
## => "*Hello* world" "*Green* 44" "*Hot* Beer" "*Bip* 6t"
library(stringr)
stringr::str_replace(A, "([[:alpha:]]+)", "*\\1*")
stringr::str_replace(A, "(\\p{L}+)", "*\\1*")
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