Win32::API doesn't build in 64-bit mode. You can use 32-bit Perl just fine on 64-bit Windows, but you need to be aware that you are running inside the WOW64 (Windows on Windows64) environment, which will redirect parts of the file system and registry, so you don't see all parts of the system.

Note also that you cannot call 64-bit DLLs from 32-bit code and vice versa.