the perl API that comes from writing modules that use XS to interface to
C.
-=head2 IPv6
-
-Clean this up. Check everything in core works
-
-=head2 shrink C<IO>s
+=head2 shrink C<PVBM>s
By removing unused elements and careful re-ordering, the structures for C<AV>s,
-C<HV>s, C<CV>s and C<GV>s have recently been shrunk considerably. C<PVIO>s and
-C<PVBM>s might have some savings to win.
+C<HV>s, C<CV>s and C<GV>s have recently been shrunk considerably. C<PVIO>s
+probably aren't worth it, as typical programs don't use more than 8, and
+(at least) C<Filter::Util::Call> uses C<SvPVX>/C<SvCUR>/C<SvLEN> on a C<PVIO>,
+so it would mean code changes to modules on CPAN. C<PVBM>s might have some
+savings to win.
=head2 Implicit Latin 1 => Unicode translation
C<my $foo if 0;> is deprecated, and should be replaced with
C<state $x = "initial value\n";> the syntax from Perl 6.
-=head2 @INC source filter to Filter::Simple
-
-The second return value from a sub in @INC can be a source filter. This isn't
-documented. It should be changed to use Filter::Simple, tested and documented.
-
=head2 regexp optimiser optional
The regexp optimiser is not optional. It should configurable to be, to allow