You say "to create a new utf8 string by decoding the value returned by "param('select')" but instead of using decode() you used encode().

You are right -- I was clearly wrong there, I should have known better and should have been more careful. I apologize.

DID YOU EVEN READ IT? AND IF YOU DID HOW YOU EXPLAIN IT?

I tried to read it, but so much of it made so little sense and was frankly erroneous. The only explanation I can imagine is that the code actually working on your website now is not the same as the code you posted. For example, when you get to this line:

unless ( grep  /^\Q$_\E$/, @menu_files )
[download]

$_ has not actually been set to anything in particular. I guess you just left out the part where you assign something to $_. And then this other thing was probably just a typo when you posted (can you spot the mistake?) -- or else it has no effect at all on the ultimate result:

for ($data) {  #Replace special chars like single & double quotes to i
+ts literally values
   s/\n/\\n/g;
   s/'/\\'/g;
   s/"/\"/g;
   tr/\cM//d;
}
[download]

When you can figure out how to post your code correctly, without silly mistakes like this, you'll get a better quality of response (and other monks will be less critical of your posts).

No matter. I'm happy for you that you have something working -- really. (But personally, I would get rid of the "char-by-char.js" display approach; it's way too slow for the amount of text in each file.)