filebrowserUploadUrl does not work in custom CGI program

I'm creating a file manager for a custom CGI program (it's Open Text's Livelink if interested to know):

CKEDITOR.replace( 'textfield',
{
customConfig : '/img/wikiext/js/ckeditor_config.js'
,filebrowserBrowseUrl : '?func=ll&objId=79416&objAction=RunReport'
,filebrowserUploadUrl : '?func=wiki.uploadimg'
});

In its thread log I found:
QUERY_STRING = 'func=wiki.uploadimg&CKEditor=textfield&CKEditorFuncNum=2&langCode=en'

However, the CGI program could not find parameter "func", which is the entry point of the script.

The filebrowserBrowseUrl works fine. I understand the difference between these two are "GET" and "POST", right? could this be the root problem? Any idea?

Thanks a lot.