package Sort;

# my($a,$b); # <<-- can't do that in this package

sub my_num_sort {
    my $list_ref = shift;
    # return as a list ref for efficiency
    return [sort { $b <=> $a } @$list_ref];
}

package main;

# my($a,$b); # <<-- you can do this in this package (no sorts)

my @list = ( 10, 42, 66, 1, 81, 32 );

# pass and return as a list ref for efficiency
my $sorted = Sort::my_num_sort(\@list);

print "$_ " for @$sorted;