I'd suggest using the goto &subroutine syntax for this case:

sub new
{
    if (@_ == 2) { goto &new_1; }
    elsif (@_ == 1) { goto &new_2; }
    else { warn "bad parameter..."; }
}
[download]

The benefit of this is that in every respect (e.g. for caller or croak) it looks like new_1 (or new_2) have been called directly - and not through new.

-- Hofmator