# \b equivalent:
(?(?<=      \w)     # if there is a word character left
      (?!   \w)     #    then there must be no word character right
  |   (?=   \w)     #    else there must be a  word character right
)

# \B equivalent:
(?(?<=      \w)     # if there is a word character left
      (?=   \w)     #    then there must be a  word character right
  |   (?!   \w)     #    else there must be no word character right
)