code: function interpolate (code) {
        return code.replace(/(\\?)([$=&])\{([^\}]+)\}/g, function (match, backslash, symbol, expression) {
          if (backslash) {
            return symbol + '{' + expression + '}'
          }
          if (expression === 'block') {
            expression = 'scope.block.call(cache,scope)'
            useCache = true
          } else {
            expression = scopify(expression, true)
          }
          if (symbol === '$') {
            if (!escapeHtmlVar) {
              escapeHtmlVar = 'ltl' + varIndex++
            }
            return "'+" + escapeHtmlVar + '(' + expression + ")+'"
          } else if (symbol === '&') {
            if (!encodeUriVar) {
              encodeUriVar = 'ltl' + varIndex++
            }
            return "'+" + encodeUriVar + '(' + expression + ")+'"
          } else {
            return "'+(" + expression + ")+'"
          }
        })
      }
docs: Find ={...}, ${...} and &{...} interpolations.
  Turn them into scope-aware insertions unless escaped.