Minor, but still good enough for a commit.
Signed-off-by: David Golden <dagolden@cpan.org>
Perl's C<$#array = $fill;>.
The number of elements in the an array will be C<fill + 1> after
-av_fill() returns. If the array was previously shorter then the
+av_fill() returns. If the array was previously shorter, then the
additional elements appended are set to C<PL_sv_undef>. If the array
was longer, then the excess elements are freed. C<av_fill(av, -1)> is
the same as C<av_clear(av)>.