Hi ikegami, Thanks for replying again, I looked it up in the perlapi:

SvPVX Returns a pointer to the physical string in the SV. The SV must contain a string.

seems the right api, but it still failes with the same error

As I am new to perl, and C, There is too much I need to know, I am going to step back and learn from the basics :) I will just leave this problem alone for a while.