sub param {
   my($self,@p) = self_or_default(@_);

   blah blah...

}

sub self_or_default {
    return @_ if defined($_[0]) && (!ref($_[0])) &&($_[0] eq 'CGI');
    unless (defined($_[0]) && 
            (ref($_[0]) eq 'CGI' || UNIVERSAL::isa($_[0],'CGI')) # slightly optimized for common case
            ) {
        $Q = $CGI::DefaultClass->new unless defined($Q);
        unshift(@_,$Q);
    }
    return wantarray ? @_ : $Q;
}