The B modules hook into the compiler stuff sort of but not really. All the actual low level stuff happens in perl-?.?.?/ext/B/B.xs which you get when you do a use B;. B::Deparse is just plain perl code. It doesn't access any internals (directly) and nothing in B::* will alter your program runtime (some other B:: stuff from CPAN is different but you aren't using those). I do see that perl 5.8.0 comes with B::Deparse rev 0.63 so you if you get rev 0.61 then that isn't jumping up to 5.8.0. Now the remaining obvious thing here is that since B::Deparse isn't C code it's not compiled and in general it shouldn't be able to break things. I say upgrade. Try it out and just keep a copy of your stock B/Deparse.pm file if you want to swap it back in.

__SIG__
printf "You are here %08x\n", unpack "L!", unpack "P4", pack "L!", B::svref_2object(sub{})->OUTSIDE