perl object and attribute - perl

Question

I am trying to create perl object (and its associated attributes), based on some conditions (for example the version of the object), a certain attribute is not needed (or invalid otherwise). How do I create the object, without having to specify the object twice (once for each condition).
my $obj = myobject->new (
attr1 => value1,
attr2 => value2,
attr3 => valuen,
)
Can I for example, define a variable and assign it different value based on the condition? Like this:
my $attribute = (condition)? "":'attr4 => value4';
and simply define the object like this:
my $obj = myobject->new (
attr1 => value1,
attr2 => value2,
attr3 => valuen,
$attribute,
)
This obviously will err out. But you get my idea. How do I make this work?

Answer 1

The arguments to new are just a list — just like the arguments to anything, in fact. You can do what you want with an array instead of a string.
my #attribute = $condition ? () : (attr4 => value4);
my $obj = MyObject->new(
attr1 => value1,
attr2 => value2,
attr3 => value3,
#attribute
);
You can also use a hash if order doesn't matter (which it usually doesn't for constructors) — whatever makes your code better.

Answer 2

I think my approach would be to build a hash of parameters, and pass it to the constructor once it was complete
It would look like this. I've wrapped the whole thing in a do block to limit the scope of %attr; it's not essential. of course condition has to be a compilable Perl expression
my $obj = do {
my %attr = (
attr1 => 'value1',
attr2 => 'value2',
attr3 => 'valuen',
);
$attr{attr4} = 'value4' if condition;
MyObject->new(%attr);
};