while( my $line = <INDEX>)
{
  my $search=lc($form{'searchtype'});
  chomp($search);
  chomp($line);
  lc($line);
  my($undef,$file,$user,$title,$subtitle,$location,$topbid,$text) = split(/\t/, $line, 8);

  if($search eq 'keyword')
  {
    next if( index($text, $search) < 0 &&  index($title, $search) < 0 && index($subtitle, $search) < 0 );
  }
  elsif ($search eq 'username')
  {
    next if index($user, $search) < 0;
  }

  # ...

}