davidrw wrote:

The root cause becomes apparent with these debugging statements in the constructor:

warn "default_values: " . \%default_values;
    my $self = ref($class) ? bless( \%default_values, ref($class) )
                           : bless( \%default_values, $class );
warn "self: " . $self;
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Thanks for reminding me about a trick I knew several years ago but had forgotten!