Have you tried rewriting your program to use plain old Perl objects (no Moose::Declare)

As stated above, the issue disappears when I get rid of MooseX::Declare and use plain Moose or even plain objects like this:

{
    package Foo;

    sub new {
        use Data::Dumper;
        print 'AH ', Dumper \@_;
        return bless {};
    }
}
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can you have a null grammar qr{}

I need the "objrule" to have Regexp::Grammars call the constructor, so the grammar cannot be reduced much further.