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Table of Contents
Select from the following table of contents to jump to a specific area within this README file. This is a HTML version of the README file distributed with HTTP Cookie Library.
Copyright and Header
HTTP Cookie LibraryVersion 2.1
Copyright 1996-2002 Matt
Created 07/13/96Last Modified 12/23/96
Matt's Script Archive, Inc.:

If you run into any problems while trying to configure this scripts, help is available. The steps you should take to get the fastest results, are:
      1) Read this file thoroughly.
      2) Consult the Matt's Script Archive Frequently Asked Questions:

      3) If you are still having difficulty installing this script,
          you may wish to look at the resources listed here:

Hopefully that will be able to help you solve your problems. Due to time # constraints I can no longer offer technical support for this code.

Copyright 1995 - 2002 Matthew M. Wright All Rights Reserved.

HTTP Cookie Library may be used and modified free of charge by anyone so long as this copyright notice and the comments above remain intact. By using this code you agree to indemnify Matthew M. Wright from any liability that might arise from its use.

Selling the code for this program without prior written consent is expressly forbidden. In other words, please ask first before you try and make money off of my program.

Obtain permission before redistributing this software over the Internet or in any other medium. In all cases copyright and header must remain intact.
HTTP Cookie Library is a Perl 4 and 5 compatible library which allows you to easily use Persistent Client State HTTP Cookies by allowing you to get the cookies from the environment, prepare cookies, set cookies, change the expiration date, domain and path all with easy subroutine calls.

Version 2.0 and 2.1 contain many changes, including the ability to compress multiple cookies into one, the elimination of the &PrepareCookies subroutine, and fixes allowing you to set more than one cookie at a time. The addition of character URL-encoding and the fixing of a scoping bug brought on by localizing the global variables used in this script are new to version 2.1.

NOTE: Anyone who used 2.0 and &UnCompressCookies should now change all references from &UnCompressCookies to &GetCompressedCookies. The calls to these routines are the same, however the name has been changed.

For more information on Cookies, and to see the preliminary specifications of Persistent Client State HTTP Cookies to which this library conforms, visit

There are three files included with this script:

1. README - This file; includes detailed installation instructions.
2. cookie.lib - The Perl script which generates the random phrase and displays it on your web page.
3. - An example of how to use this library.

The cookie.lib perl library is not a stand-alone CGI script. It is meant to be used in conjunction with a script that you build. It's only purpose is to facilitate the usage of client side persistent HTTP cookies. This means, in order to use this library, you should always have the following line in your script somewhere:

   require '/path/to/cookie.lib';

This will then tell Perl to retrieve this file and include it's code and subroutines in your script. Nonetheless, there are some variables which you can modify in the cookie.lib file before you place it on your system. All of these variables can be modified through special subroutines in cookie.lib so it is not necessary to edit any of them.
cookie.lib Configuration
This program contains three variables which can be modified in the library, to make it easier to use on your system. They can also be set through calling subroutines, which is explained in: 'Using this Library in Your CGI Script,' or by setting them in your main script, as they are local variables which can be modified. The subroutines provide checks to make sure the value is valid.

 $Cookie_Exp_Date = '';
  This variable defines the expiration date of your cookie. When this date arrives the browser will ask the user if they want to delete the cookie, and that it is ok to do so. This date must always be represented as:


and always has to be in GMT time. An example would be: Wed, 09-Nov-1999 00:00:00 GMT. By default, if this is not filled in, the browser will delete the cookie when the session ends. Also see &SetCookieExpDate.
 $Cookie_Path = '';
  This path defines where under your domain the cookies should be sent. For instance, if your URL is:, there is no reason for the browser to send the Cookie header to the base domain name. Therefore, you would set this to '/your_dir'; However, because this can be set through the script, set it to whatever directory will use this most often or whichever directory you want as default. If nothing is placed here, the default will be assumed to be the script or page which created the cookie. Also see &SetCookiePath.
 $Cookie_Domain = '';
 This defines the base domain to which the browse passes the cookie. If you have a domain:, and, which all will use this, you would set this variable to: ''; The following is an excerpt from the Netscape Preliminary Specifications of Persistent Client State HTTP Cookies:

"Only hosts within the specified domain can set a cookie for a domain and domains must have at least two (2) or three (3) periods in them to prevent domains of the form: ".com", ".edu", and "". Any domain that fails within one of the seven special top level domains listed below only require two periods. Any other domain requires at least three. The seven special top level domains are: "COM", "EDU", "NET", "ORG", "GOV", "MIL", and "INT"."

Also see &SetCookieDomain.
 $Secure_Cookie = '0';
 This defines whether or not you want to restrict the transmission of the cookie to a secure server. If this flag is set to '1', by default the cookies you create will only be sent to secure servers by the client. This can also be changed through &SetSecureCookie.
 @Cookie_Encode_Chars = ('\%', '\+', '\;', '\,', '\=', '\&', '\:\:', '\s');
 This defines the order in which the special characters should encoded. More info can be found in section entitled 'Character Translation Information'.
 %Cookie_Encode_Chars = ('\%', '%25',
                        '\+', '%2B',
                        '\;', '%3B',
                        '\,', '%2C',
                        '\=', '%3D',
                        '\&', '%26',
                        '\:\:', '%3A%3A',
                        '\s', '+');
 This associative array defines the characters to be translated as the keys, which can be referred to as: $Cookie_Encode_Chars{key} and the values which these characters should be translated into. More info can be found in section entitled 'Character Translation Information'.
 @Cookie_Decode_Chars = ('\+', '\%3A\%3A', '\%26', '\%3D', '\%2C', '\%3B', '\%2B', '\%25');
 This defines the order in which the special characters should be decoded. More info can be found in section entitled 'Character Translation Information'.
 %Cookie_Decode_Chars = ('\+', ' ',
                        '\%3A\%3A', '::',
                        '\%26', '&',
                        '\%3D', '=',
                        '\%2C', ',',
                        '\%3B', ';',
                        '\%2B', '+',
                        '\%25', '%');
 This associative array defines the characters to be translated as the keys, which can be referred to as: $Cookie_Decode_Chars{key} and the values which these characters should be decoded into. More info can be found in section entitled 'Character Translation Information'.
Using this Library in your CGI Scripts
HTTP Cookie Library is not meant as a standalone CGI script. It must be used in conjunction with other scripts you have written, and provides a basic outline and easy subroutines which makes implementing the cookies into your perl program easy.

Also, to give cookies to the user, the browser must be pointed to the CGI application or the CGI application must be imbedded in the HTML document through Server Side Includes or other technology, such as JavaScript. If you choose the JavaScript path, some browsers which support cookies won't be able to receive them and JavaScript users have no use for this library as it is only compatible in Perl scripted CGI applications.

 Requiring the Library

  Near the top of your Perl CGI script (or before you make the first call to a subroutine which is in cookie.lib), you will need to include the line:

   require '/path/to/cookie.lib';

If you place the cookie.lib in the same directory as your CGI script, or in a path which is defined in @INC, you can call it with:

   require 'cookie.lib';

 Subroutine Calls

  Now that you have required the library, all of the subroutines which this script contains can be used in your CGI Perl script. Here's is a summary of them, what they do and how to call them:

This function can be called as simply &GetCookies, or using arguments such as &GetCookies('cookie1','cookie2'). Calling it without arguments means that it will return a '1' if cookies are found, a 0 if they are not. This is useful, so that you can perform function like:

if (&GetCookies) {
   # Successful Code Here;
else {
   # Give them a Cookie Here;

In the above circumstance, if cookies are found, the successful code gets executed. Otherwise, you can give them a cookie. The &GetCookies subroutine then takes the cookies from the environment and places them in an associative array. This array is %Cookies. So if you have set a cookie named 'visit' with a value which contains whatever you set it for, then you would obtain this value by using the scalar variable $Cookies{'visit'}.

Now, let's say that a lot of cookies are set for your base domain and path. They would all get included in the return if you didn't specify arguments for &GetCookies. For instance, in the above example, since &GetCookies would return a value of '1' if any cookies are set, that could mess up this script, if all we want to know is if the visit cookie is set. Therefore, we would change the above program to only need to 'visit' cookie:

if (&GetCookies('visit')) {
   # Successful Code Here;
else {
   # Give them a Cookie Here;

Now, only the $Cookies{'visit'} scalar will be set and if it is not &GetCookies will return a 0 and the else { } statement will be executed.

You can check for multiple cookies to be set by &GetCookies('name1', 'name2','etc...'); However this will return a true value (1) if any of those cookies are set. You can get around this by calling them one at a time, although this is tedious.

If you have compressed your cookies with &SetCompressedCookies, you will need to look into the &GetCompressedCookies routine to do what &GetCookies does.

&SetCookieExpDate('Wdy, DD-Mon-YYYY HH:MM:SS GMT');
By default in the script, the cookie is set to expire when the browser session ends. If you wish for the cookie to expire at a later date, then all you have to do is change the date by calling &SetCookieExpDate with an argument containing the new date. The new date must be in the format as shown above, or it will not set right. The following is an example:

   &SetCookieExpDate('Wed, 09-Nov-1999 00:00:00 GMT');

If your date does not match a regular expression which checks to see if it is valid, it will return a 0. So it you catch the value, you can do:

if (&SetCookieExpDate('Wdy, DD-Mon-YYYY HH:MM:SS GMT')) {
   # Continue here.
else {
   # Do Error Stuff Here. &SetCookieExpDate failed.

For any cookies which you wish to be able to detect if the user closes the browser's session and then re-opens it, you will need to set this to a specific date.

The $Cookie_Exp_Date variable can also be changed at the top of cookie.lib, or at any point inside of the perl script which required cookie.lib, simply with the statement:

   $Cookie_Exp_Date = 'Wdy, DD-Mon-YYYY HH:MM:SS GMT';

The subroutine is provided to check the syntax of your date.

By default, this is set to the path of the script or web page which sets the cookie, so unless this has been set differently in cookie.lib to contain a value, you need not call this function. However, if you wish for those values to be passed to other scripts under the same domain, you will need to have this set to that path of the URL. For instance, if I only want my cookies passed to URLs which are at least:, I would call this function as:


You can also set the cookie path with the statement:

   $Cookie_Path = '/path/you/want/to/set';

You can place this statement anywhere in your Perl programs after you have required the cookie.lib library.

If the value of your desired domain suffix ( was assigned a different value as default, you can change this by placing a domain name in the call to &SetCookieDomain. Most of the time you shouldn't have to worry about this. Below are the rules which this script follows, taken directly from Netscape documentation:

"Only hosts within the specified domain can set a cookie for a domain and domains must have at least two (2) or three (3) periods in them to prevent domains of the form: ".com", ".edu", and "". Any domain that fails within one of the seven special top level domains listed below only require two periods. Any other domain requires at least three. The seven special top level domains are: "COM", "EDU", "NET", "ORG", "GOV", "MIL", and "INT"."

The $Cookie_Domain can also be set using the statemement:

   $Cookie_Domain = '';

You can place this statement anywhere in your Perl programs after you have required the cookie.lib library.

&SetSecureCookie('0' || '1');
This defines whether or not this cookie should be relayed only to secure servers. Calling &SetSecureCookie('1'); means that clients will only pass those cookies you have set to secure servers. Calling &SetSecureCookie('0'); means the cookies will be transferred whenever the path and domain are correct, regardless of security issues. Here is an excerpt from Netscape specs:

"If a cookie is marked secure, it will only be transmitted if the communications channel with the host is a secure one. Currently this means that secure cookies will only be sent to HTTPS (HTTP over SSL) servers. If secure is not specified, a cookie is considered safe to be sent in the clear over unsecured channels."

You can also change the value of $Secure_Cookie through a statement:

   $Secure_Cookie = 1;
   $Secure_Cookie = 0;

You can place this statement anywhere in your Perl programs after you have required the cookie.lib library.

&SetCookies('cookie_name1', 'cookie_value1', ..., 'cookie_namen', 'cookie_valuen');
This function has been completely changed since Version 1.1.1, except for the fact that it actually does set the cookies. There is no longer a call to &PrepareCookies, but rather &SetCookies does it all.

If you wish to set the cookies name and email, and have the values of these cookies in the variables $name and $email, you would set them with the following code:

   print "Content-type: text/html\n";
   print "\n";

The first line prints out the text/html header, with one new line following it, rather than two, since the header sent to the browser is not yet complete. Then, our call to &SetCookies is made. This call will send two Set-Cookie: headers to the browser and set both of the cookies for us.

You can send as many cookies to this subroutine as you wish to set. Browsers do have a limit though, so if you are setting multiple cookies, it is suggested that you look into the &SetCompressedCookies subroutine.

&SetCompressedCookies('compressed_cookie_name', 'cookie_name1', 'cookie_value1', ..., 'cookie_namen', 'cookie_valuen');
This subroutine does almost the same thing that &SetCookies does, but instead it takes one extra argument. You call it with the name of the compressed cookie which you wish to set and then the name/value pairs of of the cookies which you wish to compress. This subroutine doesn't actually compress cookies, but it takes multiple cookies and strings them together, so to the browser they appear as one. The = signs are converted into :: and the name/value pairs are separated from each other by &, however there is no need to change these characters before hand, as they will be translated back when uncompressed.

You may be saying, why should I bother compressing cookies when it takes extra work? I can just set 50 cookies all for different things. The main reason is, that according to Netscape's specification:

"There are limitations on the number of cookies that a client can store at any one time. This is a specification of the minimum number of cookies that a client should be prepared to receive and store.
  • 300 total cookies
  • 4 kilobytes per cookie, where the name and the value combine to form the 4 kilobyte limit.
  • 20 cookies per server or domain. (note that completely specified hosts and domains are treated as separate entities and have a 20 cookie limitation for each, not combined)
Servers should not expect clients to be able to exceed these limits. When the 300 cookie limit or the 20 cookie per server limit is exceeded, clients should delete the least recently used cookie. When a cookie larger than 4 kilobytes is encountered the cookie should be trimmed to fit, but the name should remain intact as long as it is less than 4 kilobytes."

This also means that it is up to you to check and make sure that your compressed cookie will not take more than 4KB. This is not going to be a common problem most likely, though, as 4KB is 4,000 characters, which if typed out on a common 80 column screen is about 50 lines, or almost a full page of text. The 20 cookie limit on one server name is definitely a common problem, and this helps save some of this space. As cookies become more common, clients may start reaching the 300 cookie maximum more rapidly as well.

Let's take the example from &SetCookies above, with the name and email cookies we wish to set. Now, rather than taking up two cookies, we can set one cookie named user, which will contain the information stored in the name and email cookies. To do this, make you make a call like:

   print "Content-type: text/html\n";
   print "\n";

This sets a cookie named user which contains the cookies name and email. In order to uncompress this cookie, you need to use the &GetCompressedCookies subroutine explained below. It acts much like &GetCookies.

WARNING: It is a good idea not to set the compressed cookie name equal to the name of a cookie being stored in the compressed cookie. It can mess things up.

&GetCompressedCookies('compressed_cookie_name', 'cookie_name1', ..., 'cookie_namen');
This subroutine works in almost the same way as &GetCookies, except that it needs the name of the compressed cookie first, followed by the names of the cookies you wish to retrieve out of the compressed cookie. If this subroutine is called with only the name of the compressed cookie, it will retrieve all values and place them in the %Cookies array.

For instance, if we were to take the example used in &SetCompressedCookies and we needed to only get the name of the user out of the compressed cookie, we would do something like:


Where 'user' was the name of the cookie we specified to be set when we compressed the cookies and 'name' was one of the cookies we compressed into 'user'. The value of name can now be retrieved from $Cookies{'name'}.

Or if you wished to get every cookie out of the compressed cookie, you can simply say:


And now $Cookies{'name'} and $Cookies{'email'} are set.
Character Translation Information
Version 2.1 of the HTTP Cookie Library introduces some simple character URL-encoding which eases the use and fixes some common problems with cookies. Previously, cookies would often not be set if they included spaces, semi- colons, and a few other special characters. There was also the problem found if information contained two :: or an & and you tried to compress the cookies, because those two characters are used for the compression sequence that HTTP Cookie Library uses.

According to Netscape's Persistent Client State HTTP Specification:

"This string is a sequence of characters excluding semi-colon, comma and white space. If there is a need to place such data in the name or value, some encoding method such as URL style %XX encoding is recommended, though no encoding is defined or required."

HTTP Cookie Library does use the URL style %XX (also known as hex) encoding to ensure that these characters are not lost and that the cookie is set.
Any Examples Available?, an example of how to use some of the features in this library comes bundled with the script. Hopefully the docs have been written extensively enough and the library commented enough (this is the most commented and well-documented script at MSA) that it should be fairly easy to figure out.
Any Examples Available?
There are many other cookie resources available on the Internet. Below are just a few that are the most useful and should help you out. Enjoy.

Netscape Persistent Client State HTTP Cookies Specification
The specifications to which this library conforms. Contains a lot of useful information on Cookies in general and how they can be used.

The CGI Resource Index: Documentation: HTTP Cookies
Several resources describing the use and function of cookies.
Version 2.1 12/19/96 - Changed the local() scope of global variables because they weren't setting at the top of the script right.
- Added URL-encoding to the cookies for the characters: '%', '+', ':', ',', '=', '&', '::', and space. More on this explained in the section, 'Character Translation'.
- &UnCompressCookies changed to &GetCompressedCookies, making more sense.
- &SetCookieExpDate fixed to allow a blank date.
Version 2.0 11/28/96 - &SetCookieExpDate still not working right, and finall fixed.
- &SetCompressedCookies and &UnCompressCookies subroutines added so multiple cookies can be set as one cookie and take up less room in the cookies.txt file.
- &PrepareCookie replaced by changing &SetCookies to do all of the work. This subroutine now actually takes values and sets them.
- Multiple cookied can be set now. A bug existed before which wouldn't set all of the cookies.
- Checking now done when setting cookie domain so you can know if it will work. Based on information in Netscape's Specifications.
Version 1.1.1 07/15/96 Andy Kington pointed out that the ExpDate Year should be represented as YYYY instead of YY
Version 1.1 07/14/96 - Added secure option and routines.
Version 1.0 07/14/96- First Version Released :: HTML Form to Email Processor
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