$tpid = open(MLOG,"tail -f $log_dir/mkisofs.log |");
&log("Started mkisofs.log tail: pid = $tpid");
  
while ($line = <MLOG>) {  
 if ($line =~ /estimate finish/) {
    $line =~ s/^\s+//; #remove leading whitespace
    $perc = (split(/\s+/, $line))[0];
    chop($perc); #get rid of the "%"
    $perc = sprintf("%3.0f", $perc);
    $progress_label -> configure(-text => "Completed: $perc%");
    $progress_scale -> set($perc);
    $main->update;
    }
    last if $line =~ /extents written/;
  }
  
kill('TERM', $tpid); #kill the tail process
close(MLOG);