How to use combined-stream

function saveBundle(b, vars, sourceName, dest) {

  var bundleStream = combinedStream.create();
  bundleStream.append(b.bundle());
  bundleStream.append(vars);

  return bundleStream
    .pipe(source(sourceName))
    .pipe(gulp.dest(dest));
}

gulp.task('vendor', function() {
  var b = browserify({
    debug: false
  });

  var libs = getVendorLibs();
  var vendorsConfig = require('./vendorsConfig.json');
  var exposedVariables = combinedStream.create();
  libs.forEach(function(l) {
    b.require(l.require);
    exposedVariables.append('var ' + l.expose + ' = require("' + l.require + '");' + os.EOL);
  });

  return saveBundle(b, exposedVariables, paths.dest.vendorBundle, paths.dest.bundles);
});

gulp.task('server', function() {
  var viewComponets = getViewComponents();

  var b = browserify();
  b.transform(reactify);

  var libs = getVendorLibs();
  libs.forEach(function(l) {
    b.external(l.expose);
  })

  var exposedVariables = combinedStream.create();
  viewComponets.forEach(function(c) {
    b.require(c.fullPath, {
      expose: c.name
    });
    exposedVariables.append('var ' + c.name + ' = React.createFactory(require("' + c.name + '"));' + os.EOL);
  })

  return saveBundle(b, exposedVariables, paths.dest.serverBundle, paths.dest.bundles);
})

gulp.task('kg', function () {
 var fs = require('fs');
 var kgInfo = JSON.parse(fs.readFileSync('./kg.log'));
 var version = packageInfo.version;
 var CombinedStream = require('combined-stream');
 var stream = CombinedStream.create();
 stream.append(gulp.src('./build/runtime-debug.js')
  .pipe(rename('runtime.js'))
  .pipe(replace('"xtemplate/' + version + '/runtime"', '"kg/xtemplate/' + version + '/runtime"'))
  .pipe(gulp.dest(kgInfo.dest))
  .pipe(replace(/@DEBUG@/g, ''))
  .pipe(uglify())
  .pipe(rename('runtime-min.js'))
  .pipe(gulp.dest(kgInfo.dest))
  .pipe(gulp.dest(kgInfo.dest)));
 stream.append(gulp.src('./build/index-debug.js')
  .pipe(rename('index.js'))
  .pipe(replace('"xtemplate/' + version + '/index"', '"kg/xtemplate/' + version + '/index"'))
  .pipe(replace('"xtemplate/' + version + '/runtime"', '"kg/xtemplate/' + version + '/runtime"'))
  .pipe(gulp.dest(kgInfo.dest))
  .pipe(replace(/@DEBUG@/g, ''))
  .pipe(uglify())
  .pipe(rename('index-min.js'))
  .pipe(gulp.dest(kgInfo.dest))
  .pipe(gulp.dest(kgInfo.dest)));
 return stream;
});

gulp.task('components', function() {
  var viewComponets = getViewComponents();
  var libs = getVendorLibs();

  viewComponets.forEach(function(c) {
    var b = browserify();
    b.transform(reactify);

    b.require(c.fullPath, {
      expose: c.name
    });

    libs.forEach(function(l) {
      b.external(l.expose);
    })

    var exposedVariables = combinedStream.create();
    exposedVariables.append('var ' + c.name + ' = React.createFactory(require("' + c.name + '"));' + os.EOL);

    return saveBundle(b, exposedVariables, c.name + '.js', c.destDir);
  })
})

gulp.task('xtemplate-standalone', function () {
 var CombinedStream = require('combined-stream');
 var combinedStream = CombinedStream.create();
 var packages = {};
 var fullName = 'xtemplate/' + packageInfo.version;
  var standaloneDebugJs = mod + '-standalone-debug.js';
  var modWrap = wrap[mod];
  combinedStream.append(gulp.src(path.resolve(src, js))
   .pipe(modulex({
    modulex: {

gulp.task('xtemplate', function () {
 var CombinedStream = require('combined-stream');
 var combinedStream = CombinedStream.create();
 var packages = {};
 var fullName = 'xtemplate/' + packageInfo.version;
   excludeModules = [fullName + '/runtime'];
  combinedStream.append(gulp.src(path.resolve(src, js))
   .pipe(modulex({
    modulex: {