Grep and egrep. Does anything do what both of these do?

Question

I use grep and egrep countless times daily but once in awhile I come up with a problem that grep can do part of and egrep can do the other part but neither can do both.

Maybe I just need the syntax?

I have a file with 3 digit codes something like this:
001003009000000000
002004008997999000
... etc etc

I want to find lines with the same code repeated so:

grep '00\([0-9]\).*00\1'

will find it but not necessarily in the correct format. E.g. it will incorrectly identify '001030010' even though the codes are 1, 30 and 10.

I would like to use: grep '00\([0-9]\)\(...\)*00\1'
but the wildcard does not apply to groups in grep. And egrep cannot backreference a match in the form \n.

How can it be done?

I've read the manuals. They seem to indicate that it can't be done. I'd like to know if there is another way.

Answer 1

Here is the manual page to grep maybe this can help you http://www.linuxcommand.org/man_pages/grep1.html

and this one is to egrep
http://www.nada.kth.se/cgi-bin/man?p=egrep&s=1&ss=&M=