=over 4
-=item A thread exited while %d other threads were still running
+=item A thread exited while %d threads were running
(W) When using threaded Perl, a thread (not necessarily the main
thread) exited while there were still other threads running.
=item '!' allowed only after types %s
-(F) The '!' is allowed in pack() or unpack(9 only after certain types.
+(F) The '!' is allowed in pack() or unpack() only after certain types.
See L<perlfunc/pack>.
=item Ambiguous call resolved as CORE::%s(), qualify as such or use &
generally because there's a better way to do it, and also because the
old way has bad side effects.
+=item Use of freed value in iteration (perhaps you modified the iterated array within the loop?)
+
+(F) This is typically caused by code like the following:
+
+ @a = (3,4);
+ @a = () for (1,2,@a);
+
+You are not supposed to modify arrays while they are being iterated over.
+For speed and efficiency reasons, Perl internally does not do full
+reference-counting of iterated items, hence deleting such an item in the
+middle of an iteration causes Perl to see a freed value.
+
=item Use of reference "%s" as array index
(W misc) You tried to use a reference as an array index; this probably