%what_john_has = (
                    %what_all_workers_have,
                    office_space   => 20,   # needs room to maneuvre
                    hours_per_week => 35,   # needs more breaks
 );
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That's kinda like what
    my %arguments = (%$hr_defaults, %{ $hr_args || {} });
is doing in my example code: as you've written,  %what_all_workers_have is the default of what a particular worker has.