$ perl -MDevel::Peek -E 'Dump $_ for 1<<63,-(1<<63)'
SV = IV(0x559e408d8210) at 0x559e408d8220
  REFCNT = 1
  FLAGS = (IOK,pIOK,IsUV)
  UV = 9223372036854775808
SV = IV(0x559e408d83c0) at 0x559e408d83d0
  REFCNT = 1
  FLAGS = (IOK,pIOK)
  IV = -9223372036854775808

$ perl -MJudy::L=Set -E 'say Set($j, $_, 1) for 1<<63,-(1<<63),0'
94434583711008
Coercing -9223372036854775808 to 0. Can't use negative values as keys. at -e line 1.
94434579767256
94434579767256