slim language definition

i have this basic language definition for the slim templating language. it basically works but lacks some specific features that would need dealing with indentation of previous lines and i don't know how to approach that.

for example, slim turns the following

p
  |
    This is a test
    of the text block.

into

<p>This is a test of the text block.</p>

if somebody knows how to have | enter the HL_STRING state and keep it for all following lines with a higher indentation, please teach me.