Hi

Hash::FileHash isn't the same as Hash::FieldHash

http://pass.cpantesters.org/distro/H/Hash-FieldHash.html

says version 0.10 works on perl 5.8.5

http://search.cpan.org/dist/Hash-FieldHash/Changes

says nothing functional was changed, only tests/supporting utils

http://search.cpan.org/diff?from=Hash-FieldHash-0.10&to=Hash-FieldHash-0.12

supports what Changes says

So you can install 0.10 for now with cpan GFUJI/Hash-FieldHash-0.10.tar.gz

Or you can take Corion's advice, and copy/paste the definition of SvIS_FREED to compat58.h or compat58.xsi

#define SvIS_FREED(sv)  ((sv)->sv_flags == SVTYPEMASK)
[download]

To find when it changed http://perl5.git.perl.org/perl.git?a=search&h=HEAD&st=free&s=SvIS_FREED

To find what it is http://perl5.git.perl.org/perl.git?a=search&h=HEAD&st=grep&s=define%20SvIS_FREED

You should forward a full bug report to GFUJI , or better yet a patch, I'm sure he'll want to improve compat58.h compat58.xsi