cat $file | tr [:upper:] [:lower:] | sed 's/<pattern1>/<pattern2>/
Although I suspect what you want to be doing is something like, $_ =~ s/PROJECT_RIGHTS/PROJECT_RIGHTS/gi
(the 'i' says ignore case)
-- It's not pessimism if there is a worse option, it's not paranoia when they are and it's not cynicism when you're right.