Why not take a slightly different approach. Constantly read the file, but only process complete lines. Something like this:

my $buff;
my $data;

while (1) {
  if (read(MUFFINLOG, $buf, 1024)) {
    $data .= $buf;
    while ($data =~ /\n/) {
      my $line;
      ($line, $data) = split /\n/, $data, 2;
      # process the line of data that is in $line
    }
  }
}
[download]

Perl Training in the UK <http://www.iterative-software.com>