Dump produces something like this on values that core dump with size() (the Scalar::Util here is due to me including it for more testing since my first post. Others have come from core pragmas such as warnings):

SV = IV(0x15fe438) at 0x15fe448
  REFCNT = 2
  FLAGS = (ROK)
  RV = 0x15cfc58
  SV = PVMG(0x15b8c50) at 0x15cfc58
    REFCNT = 2
    FLAGS = (POK,pPOK,SCREAM,VALID,OUR,EVALED)
    COP_LOW = 253
    COP_HIGH = 268
    PV = 0x1581bc0 "$VERSION"\0
    CUR = 8
    LEN = 16
    OURSTASH = 0x15c94e8    "Scalar::Util"
    RARE = 12
    PREVIOUS = 0
    USEFUL = 253
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I'm using Devel::Size 0.79, which is the latest on CPAN (including development releases).