use IO::Select;
open (F, 'tail -f somefile.log |') or die;
$select = IO::Select->new(*F) or die "Unable to create select object";
while(<F>) {
   $lastrec = "matt: ".$_;
   print $lastrec;
   while (! $select->can_read(1)) {
      print $lastrec;
   }
}