Associating data to text files
===

I need a good way to the following:

I have several text files, I need to be able to associate to some lines other data

E.g.

Text file:

    Line1
    Line2
    ...
    ...
    Line98

Additional data:

    Line1    |This is additional data
    Line2    |associated with line1 till line2
    ...
    ...
    Line98


I don't want to modify the text files, so I'm going to need to store this information in another file. Notice that the text files might change, so keeping track of the number of the lines isn't a safe way to do what I need.

Any suggestion?
