Well, the simplest way to tail a file is to actually just use tail. But I guess this would only work if you are on a Unix platform. You didn't mention what platform you were on, but for those who might find this useful:

my @lines=`tail logfile.txt`;
[download]

One line - can't get much simpler than that. By the way, those are back quotes, not single quotes. If you've never used them before, backquotes will execute whatever is within them like it is at the command prompt, then will return the resulting lines as an array. And whatever command you send has to exist on your system. I really don't know what backquotes do on Mac or Win.