Function with record type as argument

In a followup to an earlier question from today from another person, is
it possible to create and use a function that takes as input a generic
"record"?  Specifically, how would I use a function like:

create or replace function perl_columns(record) returns text as $a$
    my ($rec)=@_;
    my $xml_ex = '';
    foreach my $tag (keys %$rec) {
        $xml_ex = "<$tag>" . $rec->{$tag} . "</$tag>\n";
    }
    return $xml_ex;
$a$ language plperlu;

Thanks,
Sean