for my $artistkey (0..$#is_guest) {
   # Don't do anything if the artist is not a guest
   next if ($is_guest[$artistkey] == 0);
 
   # IF the artist exists, we need only to update some information
   my $sth = $dbh->prepare("SELECT FROM artists (alias) WHERE alias = ?");
   $sth->execute($artist_alias[$artistkey]);

   # The Part In Question:
   if ($sth->rows >= 1) {       
      my $sth = $dbh->prepare("UPDATE artists SET email=? WHERE alias=?");
      $sth->execute($email[$artistkey], $artist_alias[$artistkey]);
   }
   
   # Now for Redundancy
   next if ($sth->rows >= 1);
 
   my $sth = $dbh->prepare("INSERT INTO artists (alias, email, is_guest) 
   VALUES (?, ?, ?)");

   $sth->execute($artist_alias[$artistkey], $email[$artistkey], $is_guest[$artistkey]); 
   
}

##</code><code>##

   next if ($sth->rows >= 1) {       
      my $sth = $dbh->prepare("UPDATE artists SET email=? WHERE alias=?");
      $sth->execute($email[$artistkey], $artist_alias[$artistkey]);
   }