mixins.haml

%=table_row(id, *args)
  %tr{:id => id}
    -args.each do |arg|
      %td= arg



%table
  %+table_row("row1", "col1", "col2", "col3")

mixins.html

<table>
  <tr id="row1">
    <td>col1</td>
    <td>col2</td>
    <td>col3</td>
  </tr>
</table>

Looks like a partial to me, but I think that was your point.

Interesting. I think this would be very powerful. I can imagine that together with compass this could result in a very cool web widget framework or however you would name that. How hard would it be to implement this in the Haml parser? I had a look at it just before and couldn't really tell.