$ 5.8.9/bin/perl -MDevel::Peek -e'Dump(!!1)'
SV = PVNV(0x55e2de0d1348) at 0x55e2dd477310
  REFCNT = 2147483647
  FLAGS = (IOK,NOK,POK,READONLY,pIOK,pNOK,pPOK)
  IV = 1
  NV = 1
  PV = 0x55e2de0d2320 "1"\0
  CUR = 1
  LEN = 8

$ 5.8.9/bin/perl -MDevel::Peek -e'Dump(!!0)'
SV = PVNV(0x55aeb71e8320) at 0x55aeb5e05da0
  REFCNT = 2147483647
  FLAGS = (IOK,NOK,POK,READONLY,pIOK,pNOK,pPOK)
  IV = 0
  NV = 0
  PV = 0x55aeb71e8300 ""\0
  CUR = 0
  LEN = 8