Hmmmm .... what's the problem?

use CGI::WML;

my $q = new CGI::WML;
print $q->param('foo'), "\n"; 

# results:
[jeffa@trinity cgi-bin]$ ./wml.cgi foo=bar
bar
[download]

UPDATE:
Be sure and wrap the param username in quotes:

param('username')
[download]

Not doing so only issues a warning however ... the param should still be fetched.

jeffa

L-LL-L--L-LL-L--L-LL-L--
-R--R-RR-R--R-RR-R--R-RR
B--B--B--B--B--B--B--B--
H---H---H---H---H---H---
(the triplet paradiddle with high-hat)