I just downloaded the DLL from here and the following code works for me now. I noticed there are 32 and 64-Bit versions of the DLL. Make sure you are using the one that matches your Perl (64 bit most likely, find out by perl -v).

use strict; 
use warnings;
use Win32::API;

my $FCWInitObject = Win32::API->Import(
'D:\ENV\USBaccess.dll', 'int FCWInitObject()',
); 
die "Error: ".( Win32::FormatMessage( Win32::GetLastError() ) ) if !$F
+CWInitObject;

my $FCWOpenCleware = Win32::API->Import(
'D:\ENV\USBaccess.dll', 'int FCWOpenCleware(int a)',
); 
die "Error: ".( Win32::FormatMessage( Win32::GetLastError() ) ) if !$F
+CWOpenCleware;

my $pointer = $FCWInitObject->Call();
print "Pointer $pointer\n";

my $success = $FCWOpenCleware->Call( $pointer );
print "Success $success\n";
[download]

Works in the sense that it outputs the following and does not throw an error:

Pointer 8350080
Success 0
[download]

That makes kinda sense since I don't have a device connected that could be "opened" but why does it then return a pointer in the first place?