“块”型模板功能

Using http/template is it possible to define a "block"-type function that work like the built-in define or range? For example, I'd like to make a function that works like:

<div class="page">
  {{doThing}}
    Large amount of text here...
  {{end}}
</div>

I know I can make it work with {{ doThing "Large amount of text here..." }}, but that's not quite what I want.

It is not possible to write a block-type function that works like the built-in define or range actions.