My perl-5.10.0 installation only contains a DynaLoader.o

Are you sure ? My 5.10 installations don't contain either DynaLoader.a or DynaLoader.o. There's a DynaLoader.o in the build tree - but not anywhere in the perl installation that I can see.

For pre-5.10 I find that auto/DynaLoader/DynaLoader.a exists.

Cheers,
Rob