Access to query param with dashes in the name

Hi,
for the http header Nginx Nginx convert the dashes in the header name
to
underscores.
I have a query string with a param with a dash in the name, but i can’t
see
it with $arg_PARAMETER variable.
There is a way to have the value of this parameter in a variable?
For example my query string is:
response-content-disposition=attachment
I know i can parse manually the query string, but I think if there is an
Nginx embeded function, this function could by faster than a manual
parsing.
Regards,

Luca

Posted at Nginx Forum:
http://forum.nginx.org/read.php?2,241144,241144#msg-241144