sub make_sort_sub {
    my $coderef = shift;
    my $hashref = shift;
    my $sort_sub = sub { something goes here }
    return $sort_sub;
}

my %hash = ( a => 5, b => 4, c => 3 );
my $keys_by_value = make_sort_sub(
    { $hashref->{$a} <=> $hashref->{$b} },
    \%hash);
my @keys_sorted_by_value = sort $keys_by_value %hash;