my ($self, %values) = @_;  # we're being passed a hash so let's treat it like a hash
my ($tree, $messageNum, $messageText) = @values{qw/tree messageNum messageText/};

##</code><code>##

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};    
     }
}

##</code><code>##

{
   my @paramNames = qw/tree messageNum messageText/;
   sub new {
        my ($self, %values) = @_;
        validateParams(\%values, @paramNames);
        my ($tree, $messageNum, $messageText) = @values{@paramNames};
   }
}