I have received a report from a user saying that Storable no longer
compiles with perl5.00554, due to "sv_undef" being undefined.
I don't have that version around (I use only stable versions nowadays),
but if I remember correctly, the sv_undef -> PL_sv_undef change occurred
at 5.005. Such a change should leave the
#define sv_undef PL_sv_undef
around for at least ONE stable main releases (i.e. up to 5.006) past
the change point, and only remove it definitively from 5.007 and above,
to leave time to legacy code to adapt.
Storable won't compile out-of-the-box with 5.00554.
Is using PATCHLEVEL and SUBVERSION in a #if test stable in time (i.e.
officially supported) to handle portability of XS code between various
versions of the Perl run-time API?