my $tnt = [
           "http://www."    ,
           "https://www."   ,
          };

my $implode_url = sub {
    my ($url) = @_;
    my $len = scalar(@$tnt);
    for( my $i = 0 ; $i < $len; $i++) {
        $url =~ s/$tnt->[$i]/chr($i+1)/eg;  # +1 to avoid \0
    }
    return $url;
};

##</code><code>##

while( $u = <STDIN> ) {
    for( $i=1; $i < length($u)-1; $i++ ) {
        for ($j = 0; $j < length($u)-$i ; $j++ ) {
        $s = substr($u, $j, $i)
        $matches($s) += ( $u =~ m/$s/g );
    }
}

# now loop over %matches finding top 30 of:
#     $matches($key) * length($key)
#