BrowserUK's response is good, I guess, but I want to offer the following because it uses an interesting but rarely used feature of perl.

sub which_obj
{
    # examine the calling sub's 'wantarray':
    defined( (caller(1))[5] ) ? $_[0]->copy : $_[0]
}
[download]

sub foo
{
    . . .
    my $obj = $self->which_obj;
    . . .
}
[download]