#sort -t ","  -k 4,6 File.txt 
sub custom {
    my ($a4,$a6) = (split(',',$a))[4,6];
    my ($b4,$b6) = (split(',',$b))[4,6];
    
    return ($a4 == $b4)?$a4 <=> $b4:$a6 <=> $b6
}

# open(my $fh, File.txt) or die "Unable to open File.txt: $!";
# DATA used for convenience
my @result = sort custom <DATA>;

print @result,"\n";

__DATA__
11,22,33,44,55,66,77,88,99
9,1,2,3,4,5,6,7
2,3,4,5,6,7,8,9
1,2,3,4,5,6,7,8
0,0,0,0,0,0,0,0
1,2,3,5,5,6,7,8
1,2,3,4,5,7,7,8

##</code><code>##

0,0,0,0,0,0,0,0
9,1,2,3,4,5,6,7
1,2,3,4,5,6,7,8
1,2,3,5,5,6,7,8
1,2,3,4,5,7,7,8
2,3,4,5,6,7,8,9
11,22,33,44,55,66,77,88,99