or does the use base take care of this?

base does not prevent you from overriding the parent's constructor. Nor does it prevent you from doing something silly like blessing the object twice. Fix: 
package Child;
...
sub new {
    my ($class, $arg1, $arg2, $arg3) = @_; 
    my $self = $class->SUPER::new($arg1, $arg2);
    $self->{arg3} => $arg3;
    return $self;
}
...

[download]

Also - is there a difference between

Yes:

In reply to Re: Inheritance - calling parent constructor by ikegami
in thread Inheritance - calling parent constructor by bob_dobalina

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