sub add_stuff_to_file {
    my ($filehandle, $stuff) = @_;
    my $i = $stuff->iterator();
    while ($i->hasNext()) { 
         print $filehandle $i->next();
    }
}

##</code><code>##

sub add_stuff_to_file {
    my ($filehandle, $stuff) = @_;
    ($stuff->can('iterator')) || die "Stuff must be iterable";
    my $i = $stuff->iterator();
    ($i->can('hasNext') and $i->can('next')) 
      || die "Stuff's iterator must be an Iterator";
    while ($i->hasNext()) { 
         print $filehandle $i->next();
    }
}