I think the problem is that you are taking a reference to the %default_values hash, instead of making a copy of it. Try this: 

    my $self = ref($class) ? bless( +{ %default_values }, ref($class) 
+)
                           : bless( +{ %default_values }, $class );

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In general, 
+{ %hash }

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makes a (shallow) copy of %hash and returns a reference to the copy. (The leading + is not strictly necessary, but there are situations in which perl misconstrues the curlies as a block instead of an anonymous hash(ref) constructor, so I've gotten in the habit of disambiguating such expressions with a unary +.)

Likewise, 

[ @array ]

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makes a (shallow) copy of @array and returns a reference to the copy.

the lowliest monk

In reply to Re: Wrong Error Message When Testing for Failure of Constructor by tlm
in thread Wrong Error Message When Testing for Failure of Constructor by jkeenan1

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