I'm trying to install Tk module with the cpan shell 'perl -MCPAN -e shell' command (install Tk). Problem is it fails as it cannot find the X include files. I assume these are then the *.h files, which in my kubuntu is in '/usr/X11R6/include/X11' directory. So is there a way to add new path to the selection what 'install Tk' command uses to find the include files?