Hello,

I installed Judy::L and ran your one-liner. I got the same output you did.

I know nothing of the module, but are you sure it's an error and not just a warning? You can print the value of $j, which suggests it is.

$ perl -MJudy::L=Set -E 'Set($j, 1<<63, 123); say $j'

Coercing -9223372036854775808 to 0. Can't use negative values as keys.
+ at -e line 1.
105553159750592
[download]

Hope this helps!