code: function replaceRequired(fns, brstars, replacer) {
      var keys = Object.keys(fns)
      if (!keys.length) return
  
      keys.forEach(function(name) {
        var source = fns[name]
  
        source = resolve.sync(source, {
          basedir: dirname
        })
  
        if (!source) return
        var index = brstars.indexOf(source)
        if (index === -1) return
  
        replacer([name], function(node) {
          if (!node.arguments.length) return
          var value = evaluate(node.arguments[0])
          if (!value) return
  
          value = require(source)(value)
          debug('replacing for: %s = %s', name, source)
          replaceCount += 1
          hijack(node, value)
        })
      })
    }
docs: x = require('x'); x('string')