I have found then, that my XS is perfect. Wrapping this function deeper in XS doesn't help - the ENOSYS persists. Funny thing is that compiling a C program with -ldxxx -lsrl -lLiS works, while having these same libraries in the Makefile.PL does not enable these funcs properly, it seems. I wonder, how I can trace this process better to see where the error is coming from, perhaps "what" function exactly is not implemented? It could be other than the actual target routine. Is including those libraries in Makefile.PL enough? Any other tips on finding out what's going on here? I feel rediculous, but it's stumped me and all the XSing around I can think of is not helping me find the cause. I even tried swig, but quickly opted out for the simplicity and nice-ness of XS. Thanks, cb921