sub thing {
    my ( $ref, $sort_by ) = @_;
    my %sort_sub
        = ( thing1 => sub { $ref->{$a} <=> $ref->{$b} },
            thing2 => sub { $ref->{$a}->[CON] <=> $ref->{$b}->[CON] },
            etc    => sub { 'and so forth' },
          );
    my $sorter = $sort_sub{$sort_by};
    for my $key ( sort $sorter keys %{$ref} ) {
        # ...
    }
}