My dll.exp file is only 726 bytes. However, it is only created AFTER I run dmake. From the messages that I'm getting, it seems that dll.exp is an output file that is created from running a file called Constants.def.

This is where things go wrong in dmake. Notice the first line:

dlltool --def Constants.def --output-exp dll.exp
g++ -o ..\blib\arch\auto\Win32\GUI\Constants\Constants.dll -Wl,--base-file -Wl,dll.base -mdll -s -L"C:\strawberry\perl\lib\CORE" -L"C:\strawberry\c\lib" Constants.o
Constants.res -Wl,--image-base,0x370e0000 C:\strawberry\perl\lib\CORE\libperl510.a -lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32 -ladvapi32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr -lwinmm -lversion -lodbc32 -lodbccp32 dll.exp
dll.exp: file not recognized: File format not recognized
collect2: ld returned 1 exit status
dmake: Error code 129, while making '..\blib\arch\auto\Win32\GUI\Constants\Constants.dll'
dmake: Error code 255, while making 'subdirs'

To me it seems like dlltool.exe is trying to create dll.exp from Constants.def, but fails and therefore produces a wrongly formatted dll.exp. These are also in the same directory by default.

If anyone wants to see the two files, you can download them from this link:
http://rapidshare.com/files/438513360/DllexpConstantsdef.rar

Again, thanks for helping me out on this!
- Cbeppe