<!--#format expr="Hello world" formatter="StructuredText"-->

would be equivalent to

<!--#format StructuredText-->Hello world<!--#/format-->

And

<!--#format name=MyDocument formatter="StructuredText"-->

You mean, *just* like the #var tag ? :)

would be equivalent to

<!--#format StructuredText--><!--#var MyDocument--><!--#/format-->

I think a block-level flavor of #var (#block) may be interesting. WebObjects has this as a bonus luxury. .jPS