In reply to ms153:
You are getting this sort of error because you've asked for the unsized bin "data_range" to be created for all possible values across a 64-bit value (2^^64) bins which is very large and quite frankly is going to be impossible to cover in its entirety in any reasonable amount of time.
You would be better off defining bins that cover groups of input data values in some meaningful way that is appropriate for your design requirements. The alternative code you've got that uses "others = default" is a good approach if there are specific values and ranges for the input variable that are more meaningful than others; just sample for those in a manner similar to what you've started doing with the "all_zero_bin" and "all_one_bin". Another approach would be to use a sized bin instead of unsized (use "data_range", for example, to equally distribute all possible values across just 32 bins).
By the way, your "get_data()" function will never return values above 2^^32. You'll want to concatenate two calls to $urandom() together to return a full 64-bit random variable each time.