old_contents: /**
   * Copyright (c) 2014-present, Facebook, Inc.
   *
   * This source code is licensed under the MIT license found in the
   * LICENSE file in the root directory of this source tree.
   */
  
  var fs = require("fs");
  var through = require("through");
  var transform = require("./lib/visit").transform;
  var utils = require("./lib/util");
  var genOrAsyncFunExp = /\bfunction\s*\*|\basync\b/;
  
  function exports(file, options) {
    var data = [];
    return through(write, end);
  
    function write(buf) {
      data.push(buf);
    }
  
    function end() {
      try {
        this.queue(compile(data.join(""), options).code);
        this.queue(null);
      } catch (e) { this.emit('error', e); }
    }
  }
  
  // To get a writable stream for use as a browserify transform, call
  // require("regenerator")().
  module.exports = exports;
  
  // To include the runtime globally in the current node process, call
  // require("regenerator").runtime().
  function runtime() {
    regeneratorRuntime = require("regenerator-runtime");
  }
  exports.runtime = runtime;
  runtime.path = require("regenerator-runtime/path.js").path;
  
  var cachedRuntimeCode;
  function getRuntimeCode() {
    return cachedRuntimeCode ||
      (cachedRuntimeCode = fs.readFileSync(runtime.path, "utf8"));
  }
  
  var transformOptions = {
    presets: [require("regenerator-preset")],
    parserOpts: {
      sourceType: "module",
      allowImportExportEverywhere: true,
      allowReturnOutsideFunction: true,
      allowSuperOutsideMethod: true,
      strictMode: false,
      plugins: ["*", "jsx", "flow"]
    }
  };
  
  function compile(source, options) {
    var result;
  
    options = utils.defaults(options || {}, {
      includeRuntime: false
    });
  
    // Shortcut: Transform only if generators or async functions present.
    if (genOrAsyncFunExp.test(source)) {
      result = require("@babel/core").transformSync(source, transformOptions);
    } else {
      result = { code: source };
    }
  
    if (options.includeRuntime === true) {
      result.code = getRuntimeCode() + "\n" + result.code;
    }
  
    return result;
  }
  
  // Allow packages that depend on Regenerator to use the same copy of
  // ast-types, in case multiple versions are installed by NPM.
  exports.types = require("recast").types;
  
  // Transforms a string of source code, returning a { code, map? } result.
  exports.compile = compile;
  
  // To modify an AST directly, call require("regenerator").transform(ast).
  exports.transform = transform;
  
new_contents: /**
   * Copyright (c) 2014-present, Facebook, Inc.
   *
   * This source code is licensed under the MIT license found in the
   * LICENSE file in the root directory of this source tree.
   */
  
  var fs = require("fs");
  var through = require("through");
  var transform = require("./lib/visit").transform;
  var utils = require("./lib/util");
  
  function exports(file, options) {
    var data = [];
    return through(write, end);
  
    function write(buf) {
      data.push(buf);
    }
  
    function end() {
      try {
        this.queue(compile(data.join(""), options).code);
        this.queue(null);
      } catch (e) { this.emit('error', e); }
    }
  }
  
  // To get a writable stream for use as a browserify transform, call
  // require("regenerator")().
  module.exports = exports;
  
  // To include the runtime globally in the current node process, call
  // require("regenerator").runtime().
  function runtime() {
    regeneratorRuntime = require("regenerator-runtime");
  }
  exports.runtime = runtime;
  runtime.path = require("regenerator-runtime/path.js").path;
  
  var cachedRuntimeCode;
  function getRuntimeCode() {
    return cachedRuntimeCode ||
      (cachedRuntimeCode = fs.readFileSync(runtime.path, "utf8"));
  }
  
  var transformOptions = {
    presets: [require("regenerator-preset")],
    parserOpts: {
      sourceType: "module",
      allowImportExportEverywhere: true,
      allowReturnOutsideFunction: true,
      allowSuperOutsideMethod: true,
      strictMode: false,
      plugins: ["*", "jsx", "flow"]
    }
  };
  
  function compile(source, options) {
    var result;
  
    options = utils.defaults(options || {}, {
      includeRuntime: false
    });
  
    var result = require("@babel/core").transformSync(
      source,
      transformOptions
    );
  
    if (options.includeRuntime === true) {
      result.code = getRuntimeCode() + "\n" + result.code;
    }
  
    return result;
  }
  
  // Allow packages that depend on Regenerator to use the same copy of
  // ast-types, in case multiple versions are installed by NPM.
  exports.types = require("recast").types;
  
  // Transforms a string of source code, returning a { code, map? } result.
  exports.compile = compile;
  
  // To modify an AST directly, call require("regenerator").transform(ast).
  exports.transform = transform;
  
subject: Stop using RegExp to detect possible generator/async syntax.