I'm not sure I have a solution, but this might be something to consider. First of all you read lines two at a time. If you have a digit at position 'x', then the corresponding variable is on the next line at 'x - 1'. You could then re-write the expression to x^2 format (using a script to translate before getting to your script). I'm not sure if that's going to work if you're using a pipe though.

There are some hangups to consider. If there are no powers, is there a blank line? Probably not. Assuming that powers can also be expressions, then you probably need to look at where the first column starts.

Hope that might have helped in some way.