As already said, the interfaces concept (names and types of WiFi interfaces e.g.) is critically changed in Win7 compared to old WinXP. That is why the old Net::Libdnet 0.01 works fine under WinXP, but cannot properly access and build interfaces structures (hashes) under Win7. In best case, null pointers are returned from Net::Libdnet 0.01 under Win7. In worst case, a memory access violation occurs resulting crash of the perl application.