sub validateParams {
     my ($data, @paramNames) = @_;
     die "first argument to validateParams must be a hash" unless ref $data eq 'HASH';
     my $expect_count = @paramNames;
     my $actual_count = keys %$data;
     die "incorrect number of parameters - expected $expect_count, got $actual_count" unless $expect_count == $actual_count;
     for my $name (@paramNames) {
         die "parameter $name missing or undefined" unless defined $data->{$name};    
     }
}