Is there a way to prevent pkgsrc from fetching and building dependent 
packages needed by another package because it is already on the system? 
I just started using pkgsrc and am trying to install gtk, which requires 
perl5 to build. But I want to tell pkgsrc I already have a non-pkgsrc 
installation of perl5 so that pkgsrc won't install another version of 
perl on the system when I build gtk. Forgive me if the answer is in the 
Packages Documentation somewhere, but I could not easily find the answer 
to this question if it is there somewhere.

Thanks for the help