First:for($a = 0; $a <= $i; $a++){
    Second:for($s = 0; $s <= $i; $s++){
        my $d = 0;
        print $a.$t;
        print $s.$n;
        if($a!=$s){
        print "Yes.->".$a.$s.$n; last}
        print "system command \$a $a, then for \$s $s".$n;
        $d++;
    }
}