while read words.dat
do
find . -type f | xargs grep -i "${words.dat}=" 2>/dev/null >> out.log
done < words.dat 
##</code><code>##

@find = `find . -type f | xargs grep -i  sales= 2>/dev/null`;
@find = `find . -type f | xargs grep -i  price= 2>/dev/null`;
@find = `find . -type f | xargs grep -i  invoice= 2>/dev/null`;