Ah, then insert this line after the [anyway?] line:
/^...[mate].$/d

You see, what in "holed" that doesn't exist in "hello" and "world"? I picked the fourth character, which is 'e'. Add some random characters (m, a, and t) and enclose in square brackets to make them a range of forbidden characters in 4th pos (d after the last slash is the delete command). And remember, . (dot) is represent any character (in that position).

Fun, indeed.

Peace always,
<jdenny>