package base_class;
my %parameter_config = {# the same as before...};

# accessor for class-specific hash named %parameter_config:
sub parameter_config {  
  my $obclass = shift;	
  my $class   = ref($obclass) || $obclass;
  my $varname = $class . "::parameter_config";
  no strict "refs"; 	# to access package data symbolically

  %$varname = {foo=>'bar'}; 
  # this is the package-local hash %parameter_config.  
  # Just refering to '%parameter_config' should refer to 
  # %base_class::parameter_config.

}