can GREP count?

Hi there,

I need to run a search&replace script in the following example text, do some GREP stuff and replace the x within the brackets with a line number (iterations):

item[x] apple

item[x] banana

item[x] cherry

and want to obtain this:

item[1] apple

item[2] banana

item[3] cherry

Is that possible at all? Can GREP count or output i (iteration)?

Thanks for your ideas,

Ralf