my $y = WWW::Yahoo::Groups->new();
$y->login( $user => $pass );

# use ->get() which wraps ->agent->get():
$y->get( $your_desired_url );

# or get the agent (a WWW::Yahoo::Groups::Mechanize
# object, which is a subclass of WWW::Mechanize)
my $mech = $y->agent;
# and do whatever with it.
$mech->get( $your_desired_url );