Howdy!

Consider:

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

where subs new_1 and new_2 are your alternatives. You can do more detailed checking of the characteristics of the contents of @_ as needed. Of course, there is Class:Multimethods as mentioned earlier to automate this.

yours,
Michael