   ///g
 
 #-----------------------------------------------------------------------------------------------------------
+@XXX_do_bracketed_pattern = ///
+  (?: ( ^ | [^\\] ) <<\{ do >>               << do \}>> ) |
+  (?: ( ^ | [^\\] ) <<\{ do >> ( .*? [^\\] ) << do \}>> )
+  ///g
+
+#-----------------------------------------------------------------------------------------------------------
 @XXX_raw_bracketed_pattern = ///
   (?: ( ^ | [^\\] ) <<\( raw >>               << raw \)>> ) |
   (?: ( ^ | [^\\] ) <<\( raw >> ( .*? [^\\] ) << raw \)>> )

          throw new Error "unknown ID #{rpr stretch}" unless comment?
          send [ '.', 'comment', comment, ( @copy meta ), ]
        else
          send [ type, name, stretch, ( @copy meta ), ]
    #.......................................................................................................
    else
      send event

    raw_content   = $3 ? ''
    id            = @XXX_raw_id_from_content 'comment', raw_content.trim()
    return "#{$1}\x14#{id}\x13"
  #.........................................................................................................
  R = R.replace @XXX_do_bracketed_pattern, ( _, $1, $2, $3 ) =>
    $1           ?= ''
    $2           ?= ''
    $1           += $2
    raw_content   = $3 ? ''
    id            = @XXX_raw_id_from_content 'raw', raw_content
    return "#{$1}\x11#{id}\x13"
  #.........................................................................................................
  R = R.replace @XXX_raw_bracketed_pattern, ( _, $1, $2, $3 ) =>
    $1           ?= ''
