sub lcss2 {
    my ($s, $t) = @_; 
    my $z = 0;
    my $m = length $s; 
    my $n = length $t; 
    my @S = (undef, split(//, $s));
    my @T = (undef, split(//, $t));
    my @L; 
    my @ret;
 
    for my $i ( 1 .. $m ) { 
        for my $j ( 1 .. $n ) { 
            if ($S[$i] eq $T[$j]) {
                $L[$i-1][$j-1] ||= 0;  
                $L[$i][$j] = $L[$i-1][$j-1] + 1;
                if ($L[$i][$j] > $z) {
                    $z = $L[$i][$j];
                    @ret = (); 
                }
                if ($L[$i][$j] == $z) {
                    push @ret,substr($s, ($i-$z), $z);
                }
            }
        }
    }   
#    warn Dumper \@L;
    return join '*', @ret;
}