perl -MDevel::Peek -MScalar::Util=dualvar -e 'Dump !1; Dump dualvar(0, "")'
SV = PVNV(0x254ff70) at 0x7409c0
  REFCNT = 2147483647
  FLAGS = (IOK,NOK,POK,READONLY,pIOK,pNOK,pPOK)
  IV = 0
  NV = 0
  PV = 0x254ff50 ""\0
  CUR = 0
  LEN = 8
SV = PVNV(0x2550d90) at 0x2551220
  REFCNT = 1
  FLAGS = (TEMP,IOK,POK,pIOK,pPOK)
  IV = 0
  NV = 0
  PV = 0x255f610 ""\0
  CUR = 0
  LEN = 8