Okay it's starting to make sense. The following does what I would expect: 
use Readonly;

sub testvalue {

  Readonly my %hash => {h =>1};
  return \%hash;
}


my $h = testvalue();
$h->{h} = 2;

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In reply to Re^4: Hitting head against wall over Readonly compilation errors by SilasTheMonk
in thread Hitting head against wall over Readonly compilation errors by SilasTheMonk

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