See Re: Devel::BeginLift make problem and Re^4: perl-5.18.0 install problem - Part 2 (makedef.pl)

Its the same problem, Perl_hv_backreferences_p is not an part of the public api, its not exported symbol

You can get at it by recompiling perl after editing the "embed.fnc" entry for to add an A

- poM    |AV**    |hv_backreferences_p    |NN HV *hv
+ ApoM    |AV**    |hv_backreferences_p    |NN HV *hv
[download]

After that you should be able to compile Data::Swap without problems

Yes, theoretically you could through some clever copy/pasting inline a working hv_backreferences_p, but thats like c programming ... its not easy :)