Let me expand on that a little. It appears to me that you are using the funcional interface to a module as opposed to the object oriented version. If this is a CGI script and you are tring to call param from CGI.pm the following is needed.

use CGI qw(:standard);
[download]

This imports the most common functions from CGI.pm including param(). If you are using a different module please post a follow-up with more of your code.