You say you want to recursively sort an array, so I'll assume you've already done something like:

From there, you mentioned you want to recursively take 10 elements at a time. It's very easy to do this iteratively, but to specifically do it recursively as you've asked is easy, too:

my @sorted = ('A'..'Z'); # probably sort keys %some_hash;

reduce(@sorted);

sub reduce {
    my @ten = splice(@_, 0, 10); 

    return if (!@ten);       # Base case
    # return if (@ten < 10); # Or do you want to stop if < 10 elements
+?
    
    print join(',',@ten) . "\n";

    return reduce(@_); # Recursion case, remainder of array
}
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Have a look at this page on recursion if you need to brush up on your recursion theory. For example, you can switch the recursion case and the processing step, and of course you may want to return a value derived from your computations on @sorted. I leave these as an exercise to the OP. :-)