Hi :) You have tied many things together and have increased my understanding. I elimenated all the junk in my files, and created a simple one-function XS module, which returned the same results, so none of that stuff seems to be getting in the way at least. If I write a small C program using this function, and including the libraries etc, the return is the device handle as it should be. I don't, then, know how further to debug this problem - I will here admit that one might expect better C from an overripe tomato than from myself, springing from which my need for Perl. How could I check errno from the XS? I understand how to insert code there, just not 'what' code. Regarding passing the struct parameters into functions... I'm less in the dark, but I will concentrate on making the simplest functions usable, and then I will, as you say, add support as necassary. Thank you again, you have been unexpectedly helpful and kind. ceeb