Right -- of course one would usually want to make sure it goes like this (Rich36 assumes this goes without saying):

while(1) {
    my $modtime = (stat($file))[9];
    if ($modtime == $lastaccessed) {
      # The file is the same
    } else {
      # File is different; do whatever, and also:
      $lastaccessed = $modtime;
    }
    sleep 5;
}
[download]