diff --git a/README.md b/README.md
index f18e9ac..221871f 100644
--- a/README.md
+++ b/README.md
@@ -48,7 +48,7 @@ To generate the parser from JavaScript code, include the `lib/compiler.js` file
 
 To generate the parser from a command line, you need to have Java installed (so that [Rhino](http://www.mozilla.org/rhino/) — which is included in PEG.js — can run). Use the `bin/pegjs` script on Unix or `bin/pegjs.bat` batch file on Windows:
 
-    $ bin/pegjs arithmeticsParser examples/arithmetics.pegjs
+    $ bin/pegjs --export-var arithmeticsParser examples/arithmetics.pegjs
 
 This command will create the parser from the `examples/arithmetics.pegjs` file and put in into the `examples/arithmetics.js` file. The parser object will be available in the `arithmeticsParser` global variable. To learn more about the generator usage, use  the `--help` option.
 
diff --git a/Rakefile b/Rakefile
index 6179379..94e67de 100644
--- a/Rakefile
+++ b/Rakefile
@@ -27,7 +27,7 @@ def preprocess(input, base_dir)
 end
 
 file PARSER_OUT_FILE => PARSER_SRC_FILE do
-  system "#{PEGJS} PEG.parser #{PARSER_SRC_FILE} #{PARSER_OUT_FILE}"
+  system "#{PEGJS} --export-var PEG.parser #{PARSER_SRC_FILE} #{PARSER_OUT_FILE}"
 end
 
 file PEGJS_OUT_FILE => SRC_FILES do
diff --git a/bin/pegjs-main.js b/bin/pegjs-main.js
index 8f53c0d..36cd0ad 100644
--- a/bin/pegjs-main.js
+++ b/bin/pegjs-main.js
@@ -52,16 +52,17 @@ function printHelp() {
   print("Usage: pegjs [options] [--] <parser_var> [<input_file>] [<output_file>]");
   print("");
   print("Generates a parser from the PEG grammar specified in the <input_file> and");
-  print("writes it to the <output_file>. The parser object will be stored in a variable");
-  print("named <parser_var>.");
+  print("writes it to the <output_file>.");
   print("");
   print("If the <output_file> is omitted, its name is generated by changing the");
   print("<input_file> extension to \".js\". If both <input_file> and <output_file> are");
   print("omitted, standard input and output are used.");
   print("");
   print("Options:");
-  print("  -v, --version       print version information and exit");
-  print("  -h, --help          print help and exit");
+  print("  -e, --export-var <variable>  name of the variable where the parser object");
+  print("                               will be stored (default: \"exports.parser\")");
+  print("  -v, --version                print version information and exit");
+  print("  -h, --help                   print help and exit");
 }
 
 function nextArg() {
@@ -81,6 +82,9 @@ function abort(message) {
   exitFailure();
 }
 
+/* This makes the generated parser a CommonJS module by default. */
+var exportVar = "exports.parser";
+
 /*
  * The trimmed first argument is the script path -- see the beginning of this
  * file.
@@ -89,6 +93,16 @@ var args = Array.prototype.slice.call(arguments, 1);
 
 while (args.length > 0 && isOption(args[0])) {
   switch (args[0]) {
+    case "-e":
+    case "--export-var":
+      nextArg();
+      exportVar = args[0];
+      break;
+
+    case "--version":
+      printVersion();
+      exitSuccess();
+      break;
     case "-v":
     case "--version":
       printVersion();
@@ -111,12 +125,6 @@ while (args.length > 0 && isOption(args[0])) {
   nextArg();
 }
 
-if (args.length === 0) {
-  abort("Too few arguments.");
-}
-var parserVar = args[0];
-nextArg();
-
 switch (args.length) {
   case 0:
     var inputFile = FILE_STDIN;
@@ -144,4 +152,4 @@ try {
     abort(e.message);
   }
 }
-writeFile(outputFile, parserVar + " = " + parser.toSource() + ";\n");
+writeFile(outputFile, exportVar + " = " + parser.toSource() + ";\n");