Input: £ (IS UTF8? No)
Decoded: ? (IS UTF8? Yes)
Encoded: £ (IS UTF8? No)
Entities input: £
Entities decoded: £
Entities encoded: £

##</code><code>##

Input: £
Decoded: £
Encoded: £

##</code><code>##

Input: £
Decoded: £
Encoded: £

##</code><code>##

#!/usr/bin/perl
use strict;

BEGIN {
    print "content-type: text/html; charset=UTF-8\n\n";
    use FindBin qw ($RealBin $RealScript);
    use lib $FindBin::RealBin;
    chdir $RealBin;
}#BEGIN

use CGI;
my $cgi = new CGI;

print qq~
<form method=POST>
input: <input type=text name=string value="${ \$cgi->param('string') }">
<input type=submit>
</form>
~;


if ( $cgi->param('string') ) {
    use Encode qw( is_utf8 encode decode );
    print "Input: ${ \$cgi->param('string') } (IS UTF8? ";
    if ( is_utf8($cgi->param('string')) ) { print "Yes)<br>\n"; }
    else { print "No)<br>\n"; }
    my $string = decode("utf8", $cgi->param('string'));
    print "Decoded: $string (IS UTF8? ";
    if ( is_utf8($string) ) { print "Yes)<br>\n"; }
    else { print "No)<br>\n"; }
    my $octets = encode("utf8", $cgi->param('string'));
    print "Encoded: $octets (IS UTF8? ";
    if ( is_utf8($octets) ) { print "Yes)<br>\n"; }
    else { print "No)<br>\n"; }

    open( OUTF, '>utf8.txt' ) || print("Error writing file");
        print OUTF "Input: ${ \$cgi->param('string') }\n";
        print OUTF "Decoded: $string\n";
        print OUTF "Encoded: $octets\n";
    close( OUTF );

    use HTML::Entities;
    my $ent_input = encode_entities($cgi->param('string'));
    print "Entities input: $ent_input<br>\n";
    my $ent_decode = encode_entities($string);
    print "Entities decoded: $ent_decode<br>\n";
    my $ent_encode = encode_entities($octets);
    print "Entities encoded: $ent_encode<br>\n";
}#if