Although not exactly what you want: 
mysubclass->new({ myclass => { value = 23 }});

[download]
works. another solution would be to add a default value to myclass->value so that a missing initializer label does not throw a fatal error. To set a new default value, overriding the START method seems to work: 
package myclass;
use Class::Std;
my %value :ATTR( :name<value> :default(1));

1;

[download]
package mysubclass;
use base qw(myclass);

sub START {
    my ($self, $ident, $arg_ref) = @_;
    $self->set_value(123) if !defined $arg_ref->{value};
}

1;

[download]
UPDATE: original version ignored initializer labels.

In reply to Re: Overriding arguments in Class::Std superclass constructors by lima1
in thread Overriding arguments in Class::Std superclass constructors by fce2

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