Every time I call a C-function that uses arguments, I get an exception that causes Perl to quit.

What exception (what's the message you receive)? You need to investigate (maybe fire up Event Viewer, or a debugger).

You might need to make sure that your DLL is compiled with the -MD flag (or whatever perl -V:ccflags reports).

update: also, try enabling Win32::API::DEBUG and edit API.h and #define WIN32_API_DEBUG.

I did some testing, and I get a memory access violation in the perl dll, and I've tracked it down to API.xs line 651         XSRETURN_IV(lReturn);. It happens with Win32-API-0.41 and perl 5.8.4, 5.6.2, 5.8.7, but not 5.8.6, go figure. XSRETURN_IV comes from XSUB.h (official api). You should solicit help from the author and the perl5-porters. Here's the verbatim debug output

(XS)Win32::API::Call: params[0].t=1, .u=137
(XS)Win32::API::Call: parameter 0 (N) is 137
(XS)Win32::API::Call: Calling ApiFunctionInteger()
(XS)Win32::API::Call: ApiFunctionInteger returned 138
(XS)Win32::API::Call: freeing memory...
(XS)Win32::API::Call: returning to caller.
(XS)Win32::API::Call: returning 138.
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