What using strict/warning should have pointed out is that WIM_GENERIC_WRITE, WIM_CREATE_NEW are undefined. Changing that to

                           'WIM_GENERIC_WRITE',
                           'WIM_CREATE_NEW',
[download]

is garbage (probably turned into 0). You need actual numbers, like

#!/usr/bin/perl --
use strict;
use warnings;
use constant WIM_Flag_Verify => 0x00000002;
use constant WIM_Flag_Index => 0x00000004;
use constant WIM_Flag_No_Apply => 0x00000008;
use constant WIM_Generic_Read => 0x80000000;
use constant WIM_Generic_Write => 0x40000000;
use constant WIM_Open_Existing => 0x00000003;
use constant WIM_Flag_Share_Write => 0x00000040;
use constant WIM_Flag_FileInfo => 0x00000080;
use constant WIM_Compress_None => 0x00000000;
use constant WIM_Create_New => 0x00000001;
use constant WIM_Create_Always => 0x00000002;

die WIM_Generic_Write;
__END__
1073741824 at - line 16.
[download]