First, questions go in Seekers of Perl Wisdom. I moved your post there. Perl Monks Discussion is for discussions about PerlMonks.

Secondly, the modules are Win32::API and Win32::Guidgen, not win32::API, win32::GuidGen or Win32::GuidGen.

where can i get the win32::API module for windows 64 bit?

To my knowledge, there is no such module. Win32::API is very specifically for Win32. Changing it so it can handle Win64 would not be a trivial task. You'd be much better off creating an XS interface to the DLL GuidGen uses.

... or give Data::UUID a try.

Update: jand points out below that Win32 has a GuidGen() function.