+=item Reference to nonexistent or unclosed group in regex; marked by <-- HERE in m/%s/
+
+(F) You used something like C<\g{-7}> in your regular expression, but there are
+not at least seven sets of closed capturing parentheses in the expression before
+where the C<\g{-7}> was located.
+
+The <-- HERE shows in the regular expression about where the problem was
+discovered.
+
+=item Reference to nonexistent named group in regex; marked by <-- HERE in m/%s/
+
+(F) You used something like C<\k'NAME'> or C<< \k<NAME> >> in your regular
+expression, but there is no corresponding named capturing parentheses such
+as C<(?'NAME'...)> or C<(?<NAME>...). Check if the name has been spelled
+correctly both in the backreference and the declaration.
+
+The <-- HERE shows in the regular expression about where the problem was
+discovered.
+
+=item (?(DEFINE)....) does not allow branches in regex; marked by <-- HERE in m/%s/
+
+(F) You used something like C<(?(DEFINE)...|..)> which is illegal. The
+most likely cause of this error is that you left out a parenthesis inside
+of the C<....> part.
+
+The <-- HERE shows in the regular expression about where the problem was
+discovered.
+