// Keywords appear after all the rest.
	itemKeyword  // used only to delimit the keywords
	itemBlock    // block keyword
	itemBreak    // break keyword
	itemContinue // continue keyword
	itemDot      // the cursor, spelled '.'
	itemDefine   // define keyword
	itemElse     // else keyword
	itemEnd      // end keyword
	itemIf       // if keyword

	itemRightParen:   ")",
	itemSpace:        "space",
	itemString:       "string",
	itemVariable:     "variable",

	// keywords
	itemDot:      ".",
	itemBlock:    "block",
	itemBreak:    "break",
	itemContinue: "continue",
	itemDefine:   "define",
	itemElse:     "else",
	itemIf:       "if",
	itemEnd:      "end",
	itemNil:      "nil",
	itemRange:    "range",
	itemTemplate: "template",
	itemWith:     "with",
}

func (t *Tree) action() (n Node) {
	switch token := t.nextNonSpace(); token.typ {
	case itemBlock:
		return t.blockControl()
	case itemBreak:
		return t.breakControl(token.pos, token.line)
	case itemContinue:
		return t.continueControl(token.pos, token.line)
	case itemElse:
		return t.elseControl()
	case itemEnd:
		return t.endControl()
	case itemIf:
		return t.ifControl()
	case itemRange: