use strict;
use warnings;
use Plack::Request;
use Plack::Response;
use HTML::Template;

my $app = sub {

    my $tmpl = HTML::Template->new( 
        filehandle => \*DATA,
        die_on_bad_params => 0,
    );

    my $req = Plack::Request->new( shift );
    my $query = $req->parameters;
    $tmpl->param( $query );

    my $res = Plack::Response->new( 200 );
    $res->content_type('text/html');
    $res->body( $tmpl->output );
    $res->finalize;
};


__DATA__
<tmpl_if submitted>
  <h1>Hello <tmpl_var textfield> <tmpl_var textfield2></h1>
<tmpl_else>
  <form>
    <p>firstname: <input type="text" name="textfield" /</p>
    <p>lastname: <input type="text" name="textfield2" /</p>
    <p><input type="submit" name="submitted" value="Submit" /></p>
  </form>
</tmpl_if>