PVNV

• PVNV has an IV slot too (surprise!)

    perl -MDevel::Peek -le '$a = 0.5 ; $a = "1"; Dump($a)'
    SV = PVNV(0x80f7ea0) at 0x810b4c0
      REFCNT = 1
      FLAGS = (POK,pPOK)
      IV = 0
      NV = 0.5
      PV = 0x80f6090 "1"\0
      CUR = 1
      LEN = 2
  

• SvNV(sv) returns the NV value
• sv_newSVnv(some_float) creates new SvNV