Getting the last couple of rows is easy enough. Here's an example fragment that just reads the file in from STDIN:

$my( $curr_time, $prev_time );
while( <> ) {
    $prev_time = $curr_time;
    $curr_time = ( split /,/ )[1];
}
[download]

You can modify that to be a bit more robust or to open a file properly or what have you.

I'm not sure how you're calculating the percentage. Are you just dividing one number by the other?

You can print the percentage in whatever format you need using sprintf, for example:

$percentage = "%" . sprintf( "%.3f", $prev_time / $curr_time * 100 );

Or whatever your calculation is.

I'm sorry I can't be of much more help than this. If your code isn't working properly, post the fragment where the problem lies (or a test program that duplicates the problem) here and we'll try and sort through it.

If you don't have any code yet, then try your hand at the problem yourself. Worst case scenario is you're no worse off than before. :)

Good luck!

elbieelbieelbie