use strict;

sub {
  my ($this, $con) = @_;

  my $subtype = $con->param('subtype') || 'plain';
  unless ($subtype =~ /^\w+$/) {
    die "Invalid subtype!";
  }

  $con->set_header(-type => "text/$subtype");
  print {$con} "<h2>Hello</h2>";
};
