Hrmmm...I interpret this question differently.

<FORM METHOD="Post" ACTION="http://www.server.com/cgi-bin/form.pl">
<INPUT TYPE="Hidden" NAME="id" VALUE="103">
<INPUT TYPE="Submit" VALUE="Send this as a POST!">
</FORM>
[download]

As long as form.pl is a fairly standard script, it should have no problem reading the data as either a GET or a POST request.

Still, the question is confusing..are you trying to write a server? A client? Both? Neither?