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