[Regexp] a regexp question

[Levent Yilmaz]

Hello,

It sounded like a very simple problem but I couldn't come up with a 
solution. I was trying to do this with Basic Regexp in grep:

Find all lines which contain the word 'kitty'. But only those lines that 
do not have 'puppy' somewhere before 'kitty'. For instance:

my kitty is very cute
but puppy is cuter than kitty

What regular expression stands for the first line but not the second? 
Note that the other way is very easy, that is the lines with 'puppy' 
followed by 'kitty': puppy.*kitty

thank you so very much!
-Levent.


PS: What is all this spam on the list by the way?