#!/usr/bin/perl

use strict;
use warnings;

use CGI;
use Encode         qw( decode );
use HTML::Entities qw( encode_entities );

my $cgi = CGI->new();

my $val = $cgi->param('key');
use Devel::Peek;
Dump($val);
$val = decode('iso-8859-15', $val) if defined($val);

print $cgi->header('text/html; charset=iso-8859-15');
binmode STDOUT, ':encoding(iso-8859-15)';

my $val_initializer = ( defined($val)
    ? sprintf(' value="%s"', encode_entities($val, '<>&"'))
    : ''
);

print(<<"__EOI__");
<title>Test</title>
<form method="POST">
<input type="text" name="key"$val_initializer>
<input type="submit">
</form>
__EOI__

##</code><code>##

$ perl -e'print <<"__EOI__";
POST /zzz.cgi HTTP/1.0
Host: www.example.com
Content-Length: 11

key=Ch\xE2teau
__EOI__
' | nc www.example.com 80 | od -c
00000   H   T   T   P   /   1   .   1       2   0   0       O   K  \r
00020  \n   D   a   t   e   :       W   e   d   ,       2   8       A
00040   p   r       2   0   1   0       2   2   :   1   0   :   1   4
00060       G   M   T  \r  \n   S   e   r   v   e   r   :       A   p
00100   a   c   h   e  \r  \n   V   a   r   y   :       A   c   c   e
00120   p   t   -   E   n   c   o   d   i   n   g  \r  \n   C   o   n
00140   t   e   n   t   -   L   e   n   g   t   h   :       1   1   8
00160  \r  \n   C   o   n   n   e   c   t   i   o   n   :       c   l
00200   o   s   e  \r  \n   C   o   n   t   e   n   t   -   T   y   p
00220   e   :       t   e   x   t   /   h   t   m   l   ;       c   h
00240   a   r   s   e   t   =   i   s   o   -   8   8   5   9   -   1
00260   5  \r  \n  \r  \n   <   t   i   t   l   e   >   T   e   s   t
00300   <   /   t   i   t   l   e   >  \n   <   f   o   r   m       m
00320   e   t   h   o   d   =   "   P   O   S   T   "   >  \n   <   i
00340   n   p   u   t       t   y   p   e   =   "   t   e   x   t   "
00360       n   a   m   e   =   "   k   e   y   "       v   a   l   u
00400   e   =   "   C   h 342   t   e   a   u   "   >  \n   <   i   n
00420   p   u   t       t   y   p   e   =   "   s   u   b   m   i   t
00440   "   >  \n   <   /   f   o   r   m   >  \n
00453

##</code><code>##

use strict;
use warnings;

use open ':std', ':locale';
use charnames ':full';

use Encode qw( encode );
use WWW::Mechanize qw( );

# Avoiding script encoding issues.
my $val = "Ch\N{LATIN SMALL LETTER A WITH CIRCUMFLEX}teau";

my $mech = WWW::Mechanize->new( autocheck => 1 );
$mech->get('http://www.server.com/zzz.cgi');

$mech->field('key', $val);
$mech->submit();

#print($mech->value('key'), "\n");
use Devel::Peek qw( Dump );
Dump($mech->value('key'));

##</code><code>##

SV = PV(0x1167c20) at 0x11d05c0
  REFCNT = 1
  FLAGS = (TEMP,POK,pPOK,UTF8)
  PV = 0x11572c0 "Ch\303\203\302\242teau"\0 [UTF8 "Ch\x{c3}\x{a2}teau"]
  CUR = 10
  LEN = 16

##</code><code>##

SV = PV(0x1167c20) at 0x11d05c0
  REFCNT = 1
  FLAGS = (TEMP,POK,pPOK,UTF8)
  PV = 0x115bcf0 "Ch\303\242teau"\0 [UTF8 "Ch\x{e2}teau"]
  CUR = 8
  LEN = 16

##</code><code>##

SV = PV(0x1167c20) at 0x11d05c0
  REFCNT = 1
  FLAGS = (TEMP,POK,pPOK)
  PV = 0x115bcf0 "Ch\342teau"\0
  CUR = 7
  LEN = 16

##</code><code>##

"Ch\303\242teau"

##</code><code>##

#$mech->field('key', $val);
$mech->field('key', encode('iso-8859-15', $val));
$mech->submit();

##</code><code>##

"Ch\303\242teau"