#markup-start event
Use #markup-start to signal the start of a markup-region-event to a do
markup-parse. #markup-start must be used with a corresponding #markup-end
signal which refers to the same (reference-equal) event.
The following element rule reproduces the save events that triggered the rule:
element #implied signal throw #markup-start #current-markup-event output #content signal throw #markup-end #current-markup-event