a simple (i think) REGEX needed for Textmate

Question

Can someone please advise how to do this search and replace in textmate. I think I need a REGEX (but i know very little about REGEXes!)

i want to change all these bullet images to GIFs...

bullet-1.png

becomes

bullet-1.gif

and I want where the number is to be a wildcard

Answer 1

The regular expression:

bullet-(\d+).png

The replacement:

bullet-$1.gif