"How can you use 'nano' there?..."

I think perhaps my example was a little misleading. "nano" is the name of the script, and "foo.pl" is the name of the file being precessed. Think of it instead as:

perl nano some_random_file
[download]

..and it should make more sense.

"..what is the difference between time() as used by you versus liverpole's suggestion of using 'tv_interval' and 'gettimeofday'?"

Again, rtfm. As far as I can see, there is no real difference. The resolution that you get will be mostly system-dependant.

Cheers,
Darren