| how declared | behaviour |
|---|
| \define | Textual substitution of parameters is performed on the body text. No further processing takes place. The result after textual substitution is used as the filter operator's parameter. |
$set, $let, $vars, \procedure, \widget | Body text is retrieved as-is and used as the filter operator's parameter. |
| \function | The body text of the function is treated as a filter expression and evaluated. The first result is passed to the operator as a parameter. The remaining results are discarded. |