# Reset number of tries
$trycount=0;

{ 
  # Increase number of tries
  $trycount++;

  # Make sure we don't try forever
  last if ($trycount > 10)

  # Put last id + 1 in $id
  SELECT MAX(id)+1 FROM table;

  # Try to insert new row and check for errors
  INSERT INTO table (id,col1,coln) VALUES ($id,$col1,$coln);

  # Try again
  redo if (error eq "Unable to insert due to duplicate values");
}

# Handle too many tries
die "Too many tries" if ($trycount > 10);