my %fragment_exists;
sanitize_name(sub {map { $_ . "_" . $fragment_exists{ $_  }++} @_ },
              $title, ...);

##</code><code>##

my %fragment_exists;

my $fragment;
my $duplicate = '';
do {
    $fragment = sanitize_name( "$title_" . $duplicate++ );
while( $fragment_exists{ $fragment }++ );