[Koha-devel] bar code not unique

Hi, I remember reading on the list lately about the bar code not having to be unique. Well I would like to enforce it to be unique. I'm not a perl programmer, but I had a look in acqui.simple/additem.pl and I'm puzzled by the comment on line 81 saying "check for bar code # being unique". Could someone tell me what I need to do to make it verify the number being unique. Many thanks. tomasz kotula.