-NBOUND NBOUND, no ; Match "" at any word non-boundary using native charset rules for non-utf8
-NBOUNDL NBOUND, no ; Match "" at any locale word non-boundary
-NBOUNDU NBOUND, no ; Match "" at any word non-boundary using Unicode rules
-NBOUNDA NBOUND, no ; Match "" at any word non-boundary using ASCII rules
+NBOUND NBOUND, no ; Like NBOUNDA for non-utf8, otherwise match "" between any Unicode \w\w or \W\W
+NBOUNDL NBOUND, no ; Like NBOUND/NBOUNDU, but \w and \W are defined by current locale
+NBOUNDU NBOUND, no ; Match "" at any non-boundary of a given type using using Unicode rules
+NBOUNDA NBOUND, no ; Match "" betweeen any \w\w or \W\W, where \w is [_a-zA-Z0-9]