lanx:$ perl -MDevel::Peek -E'$x+=2**$_ for 0..52;Dump ($x);Dump($x+1)'
SV = IV(0x64c9edf22bb0) at 0x64c9edf22bc0
  REFCNT = 1
  FLAGS = (IOK,pIOK)
  IV = 9007199254740991
SV = IV(0x64c9edf838d0) at 0x64c9edf838e0
  REFCNT = 1
  FLAGS = (PADTMP,IOK,pIOK)
  IV = 9007199254740992