So you want to create a cookie when the page loads? I know this is a Perl forum, BUT you could do this in JavaScript very easily.

(JavaScript is very similar to Perl in syntax, and in addition, you can use the $ sign anywhere in a variable name. Or you may decided to not use it at all. It's up to you. If you like to write code that resembles perl, you can start each variable name with a dollar sign. There is absolutely no difference between a ' and " signs for declaring strings. You use whichever you like. Also, instead of using a dot to merge two strings, you must use a plus sign.)

So, anyway, you just put this in a HTML file, and it will create a cookie called "MyCookie" which expires in 5 years, and then it will read that same cookie. And if the read is successful, then it prints that cookies are working fine. So, it's a simple code. Your perl program would simply print this entire block anywhere within the HTML file, and if you want to change the value of the cookie, just make sure it's a valid string. The string declaration in JavaScript is just like in C or C++. Same syntax. Also, you may not include any special characters in a cookie value other than listed in a variable named $COOKIEJAR. So, those are the only valid characters you may use in a cookie.

The difference between localStorage is that you may store any kind of binary data in localStorage. LocalStorage is usually 10 MB in size. Cookies can only store up to 5 KB, and if your website creates more than what fits in that space, then you simply won't be able to create anymore cookies. You have to delete some in order to free up some space. Cookies also have expiration, while localStorage does not have expiration. Also, whatever you put in localStorage does not get sent back to the server with each page request. So, they are hidden. Only the JavaScript program can read and write to localStorage.

Note: Some very old browsers used in old smart phones do not support localStorage. And some browsers may have cookies turned off but localStorage is enabled! So, if it is an absolute MUST for you to store something on the visitor's computer, then you should check both cookies and localStorage to see which one is available and working.

<SCRIPT>

/* JAVASCRIPT CODE BEGINS HERE */

// DETECT COOKIES & LOCAL STORAGE
COOKIES_AVAILABLE = navigator.cookieEnabled ? 1 : 0;
STORAGE_AVAILABLE = 0; try { localStorage.getItem("X"); STORAGE_AVAILA
+BLE = 1; } catch (e) {}

$COOKIEJAR = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrst
+uvwxyz$@!?*|#&%^`~+:-., []{}()_/\\><\"'";

SetCookie("MyCookie", "Hello World!!!");

document.write( "<P>LocalStorage is " + (STORAGE_AVAILABLE ? 'ENABLED 
+and WORKING' : 'NOT WORKING, NOT SUPPORTED, or DISABLED.') );
document.write( "<P>Your browser says that cookies are " + (COOKIES_AV
+AILABLE ? 'SUPPORTED and ENABLED' : 'DISABLED or NOT SUPPORTED') );
document.write( "<P>" );

if (GetCookie("MyCookie") == "Hello World!!!")
{
  document.write("In reality, cookies are supported and are working fi
+ne!");
}
else
{
  if (document.cookie.length > 1000)
    document.write("In reality, cookies aren't working, because your c
+ookie storage is full. There are probably too many cookies.");
  else
    document.write("In reality, cookies aren't working!");
}

document.write( "<P>The cookies are = " + document.cookie );

////////////////////////////////////
//
// COOKIE & LOCAL STORAGE FUNCTIONS:

// Creates a cookie that expires in 5 years.
function SetCookie(NAME, VALUE) { var E = new Date(); E.setFullYear(E.
+getFullYear() + 5); document.cookie = NAME + "=" + VALUE + ";Expires=
+" + E.toGMTString(); }

// Returns the value of a cookie.
function GetCookie(NAME) { var i, e, s, K = document.cookie.split(";")
+; for (i = 0; i < K.length; i++) { for (s = 0; K[i].charCodeAt(s) < 3
+3; s++); e = K[i].indexOf("="); if (K[i].substring(s, e) == NAME) ret
+urn K[i].slice(++e); } return ""; }

// Returns an array of cookie names.
function GetCookieNames() {var i,S,L,C,K=document.cookie+";",SAVE=1,A=
+[];for(L=S=i=0;i<K.length;i++){C=K.charCodeAt(i);if(C==61||C==59){if(
+SAVE)A.push(K.substr(S,L));L=S=0;SAVE=(C==59)?1:0;}else if(SAVE&&C>32
+)if(L++==0)S=i;}return A;}

// Completely erases a cookie.
function DeleteCookie(NAME) {document.cookie=NAME+"=;Expires=Jan 01 19
+70 01:01:01 GMT";}

// Deletes all cookies.
function DeleteAllCookies() {var i,S,L,C,K=document.cookie+";",SAVE=1,
+CC=0;for(L=S=i=0;i<K.length;i++){C=K.charCodeAt(i);if(C==61||C==59){i
+f(SAVE){DeleteCookie(K.substr(S,L));CC++;}L=S=0;SAVE=(C==59)?1:0;}els
+e if(SAVE&&C>32)if(L++==0)S=i;}return CC;}

// Saves a value in localStorage.
function SetItem(NAME, VALUE) {try{with(window.localStorage){setItem(N
+AME,VALUE);if(getItem(NAME)==VALUE)return 1;}}catch(e){}return 0;}

// Retrieves a value from localStorage.
function GetItem(NAME) {var V=null;try{V=localStorage.getItem(NAME);}c
+atch(e){}return V;}

// Returns a list of names stored in localStorage.
function GetItemNames()    {var i,A=[];try{for(i=0;i<localStorage.leng
+th;i++)A[i]=localStorage.key(i);}catch(e){}return A;}

// Erases an item from localStorage.
function DeleteItem(NAME) {try{with(window.localStorage){setItem(NAME,
+"");removeItem(NAME);}return 1;}catch(e){}return 0;}

// Empties localStorage.
function DeleteAllItems() {try{localStorage.clear();return 1;}catch(e)
+{}return 0;}

</SCRIPT>
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