Ok, here is the cleaner self contain Perl script with inline FORM submit. Do make sure the form action value is "utf8_encode.pl" or change to your desire. For direct test, use this "【" Chinese character for example. For the result #3, I use unpack for this purpose. Previously found several ways and they give same results where single Chinese char "【" when split will become 3 char 227,128,144.

I'm still not quite understand of the explaination given. Almost getting the hand of it.

If I can get the encoding solved, then I think I should be able to get the Decode working as well.

The string match will be in separate processing where the code looks like this my ($result) = $str =~ m/\&\#12304\;(.*?)\&\#12305\;/sig;

#!/usr/bin/perl
######################################################################
+##########
#
#
######################################################################
+##########
use CGI ':standard';
use HTML::Entities; #-- for encode and decode string


(%FORM) = ();
if ($ENV{'REQUEST_METHOD'} eq "POST")
{
    my ($id);
    #-- extract the value inside param into %FORM hash
    foreach $id (param)
        {
            $FORM{$id} = param($id);
        }
} # // if post

print "Content-Type: text/html; charset=utf-8\n\n";

print "<h2>Encode UTF-8 Chinese Character Input</h2><br>";

print &input_form;


#---------------------------------------------------#
#---------------------------------------------------#
sub input_form
{
    my ($content) = "";
    
    my ($value) = "";
    if ($FORM{'data'} ne "")
        {
            $value = $FORM{'data'};
        }
        
    my ($encoded_value) = "";
    my ($process_content) = "";
    
    if ($FORM{'action'} eq "encode")
        {
            $encoded_value = $FORM{'encoded_value'};
            
            # !! attempt to do encoding inside perl but the $FORM{'dat
+a'} when split,
            # it become 3 char for Chinese char !!
            my (@arr) = split(//,$FORM{'data'});
            foreach my $c (@arr)
                {
                    $c = unpack('C*', $c);
                    $process_content .= "$c\n";
                }
        }
    elsif ($FORM{'action'} eq "decode")
        {
        }
        
    
    #-- content ---------------------------------
    $content = qq~
    <script type="text/javascript">
    function encodeCN(id) {
        var tstr = document.getElementById(id).value;
        var bstr = '';
        for(i=0; i<tstr.length; i++)
        {
            if(tstr.charCodeAt(i)>127)
            {
                bstr += '&#' + tstr.charCodeAt(i) + ';';
            }
            else
            {
                bstr += tstr.charAt(i);
            }
        }
        document.getElementById('encoded_value').value = bstr;
    }
    </script>
    
    <form id="fr_in" name="fr_in" action="utf8_encode.pl" style="" met
+hod="POST" enctype="application/x-www-form-urlencoded">
    <input type="hidden" onFocus="this.blur()" name="convert" id="conv
+ert" value="">
    <input type="hidden" onFocus="this.blur()" name="action" id="actio
+n" value="">
    <input type="hidden" name="encoded_value" id="encoded_value" value
+="">
    
    <textarea id="data" name="data" style="width:600px; height:200px;"
+>$value</textarea>    
    <br>
<xmp>
1. FORM submitted value:
$value

2. Encoded value thru JS before form submit:
$encoded_value

3. *Try to do encoding inside Perl*
$process_content
</xmp>
    

    <input type="button" value="Encode" onClick="encodeCN('data'); doc
+ument.getElementById('action').value='encode'; this.form.submit();">
    <input type="button" value="Decode" onClick="document.getElementBy
+Id('action').value='decode'; this.form.submit();">
    </form>
    ~;
    #--// content -------------------------------
    
    return ($content);
}
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