The reasons in that thread are talking about having something other than perl itself parse Perl scripts. B::Deparse doesn't parse Perl, it dumps the results of what perl itself parsed.

The only reason that B::Deparse is missing 5% (or less) is because the module is still young. Some of the bigger missing pieces were just put in place (from what I read) so I suspect that the latest version (not generally available) can successfully "deparse" quite a few working scripts such that the results are functionally identical.