my $data = retrieve_from_db($params);
if( $params->{need_html} ){
  my $html = perl2html($HTML_TMPL_FILE, $data);
  render(html => $html);
} elsif( $params->{need_json} ){
  my $json = perl2json($JSON_TMPL_FILE, $data);
  render(json => $json);
} # ...