diff --git a/man3/regex.3 b/man3/regex.3
index 0523bb124..b65799823 100644
--- a/man3/regex.3
+++ b/man3/regex.3
@@ -157,6 +157,17 @@ The match-end-of-line operator always fails to match (but see the
 compilation flag
 .B REG_NEWLINE
 above).
+.SS BSD regex matching
+.TP
+.B REG_STARTEND
+Use pmatch[0] on the input string, starting at byte pmatch[0].rm_so and ending
+before byte pmatch[0].rm_eo. This allows matching embedded NUL bytes
+and avoids a strlen() on large strings. It does not use nmatch on input,
+and does not change
+.B REG_NOTBOL
+or
+.B REG_NEWLINE
+processing.
 .SS Byte offsets
 Unless
 .B REG_NOSUB