[R] iteration introspection?

[Cere Davis]

Hi everyone,

I want to perform a regex substitution on line #1 in a file based on the 
contents of line #2.  same is true for line 11 and line 12 etc...

With the look at each line of a file rolling forward method it seems to 
me that I will not be able to use iterators like 'each' for this 
operation unless I am able to manipulate or even know of the position of 
the file pointer from within the iterator block but I don't know of a 
way to do this.

Does anyone know how I can learn what the value of my iterator is within 
  a loop?

Thanks,
Cere