You're right, a general solution would involve recursion. I don't think you need it in this case, because your tree has a specific fixed depth. But here's a recursive solution anyway:

sub tree_to_table
{
    if ( ref $_[-1] )
    {
        my $hr = pop;
        my @kv;
        tree_to_table( @_, @kv ) while @kv = each %$hr;
    }
    else
    {
        local($,,$\) = (',',"\n");
        print map qq("$_"), @_
    }
}

tree_to_table( $exception_report );
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