You got confused there, headers come after params 
#!/usr/bin/perl --

use strict;
use warnings;

use HTTP::Request::Common qw' POST ';

my %params= ('page' => 28,
         'index' => 36);

print POST('http://example.org', \%params , qw' Content-Type form-data
+ ', )->as_string;
__END__
POST http://example.org
Content-Length: 132
Content-Type: multipart/form-data; boundary=xYzZY

--xYzZY
Content-Disposition: form-data; name="index"

36
--xYzZY
Content-Disposition: form-data; name="page"

28
--xYzZY--

[download]
That still doesn't help the OP with his custom protocol

In reply to Re^2: HTTP::Request::Common : Specify POST fields separators ? by Anonymous Monk
in thread HTTP::Request::Common : Specify POST fields separators ? by odrevet

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