of upgradability. Upgrading to undef indicates an error in the
code calling sv_upgrade.
+=item Can't use %%! because Errno.pm is not available
+
+(F) The first time the %! hash is used, perl automatically loads the
+Errno.pm module. The Errno module is expected to tie the %! hash to
+provide symbolic names for C<$!> errno values.
+
=item Can't use "my %s" in sort comparison
(F) The global variables $a and $b are reserved for sort comparisons.
%hash = ( one => 1, two => 2, ); # right
%hash = qw( one 1 two 2 ); # also fine
-=item Reference found where even-sized list expected
-
-(W) You gave a single reference where Perl was expecting a list with
-an even number of elements (for assignment to a hash). This
-usually means that you used the anon hash constructor when you meant
-to use parens. In any case, a hash requires key/value B<pairs>.
-
- %hash = { one => 1, two => 2, }; # WRONG
- %hash = [ qw/ an anon array / ]; # WRONG
- %hash = ( one => 1, two => 2, ); # right
- %hash = qw( one 1 two 2 ); # also fine
-
=item Reference miscount in sv_replace()
(W) The internal sv_replace() function was handed a new SV with a