use Mojolicious::Lite;

get '/' => sub { shift->render('index') };
post '/' => sub { shift->render('index') };

app->hook(before_dispatch => sub {
  my $c = shift;

  $c->tx->req->max_message_size(1e9);
});

app->start;

__DATA__
@@ index.html.ep
<form enctype="multipart/form-data" method="post">
<input type="file" name="f">
<button>Upload</button>
</form>