perl -MDevel::Peek -e "my @a; Dump \@a, 1; printf qq[SIZE :%d\n], $#a; Dump \@a, 1"
SV = RV(0x34e158) at 0x34e148
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x276630
  SV = PVAV(0x34efb8) at 0x276630
    REFCNT = 2
    FLAGS = (PADMY)
    ARRAY = 0x0
    FILL = -1
    MAX = -1
    ARYLEN = 0x0
    FLAGS = (REAL)
SIZE :-1
SV = RV(0x34e290) at 0x34e280
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x276630
  SV = PVAV(0x34efb8) at 0x276630
    REFCNT = 2
    FLAGS = (PADMY,RMG)
    MAGIC = 0x27fde8
      MG_VIRTUAL = &PL_vtbl_arylen_p
      MG_TYPE = PERL_MAGIC_arylen_p(@)
      MG_FLAGS = 0x02
        REFCOUNTED
      MG_OBJ = 0x34e148
      SV = PVMG(0x261f18) at 0x34e148
        REFCNT = 1
        FLAGS = (GMG,SMG,pIOK)
        IV = -1
        NV = 0
        PV = 0
        MAGIC = 0x27fcf8
          MG_VIRTUAL = &PL_vtbl_arylen
          MG_TYPE = PERL_MAGIC_arylen(#)
          MG_OBJ = 0x276630
    ARRAY = 0x0
    FILL = -1
    MAX = -1
    ARYLEN = 0x34e148
    FLAGS = (REAL)