My guess is that caller simply needs improving

use Devel::Peek;
package DO;
sub A{warn@_};
*DO=\&A;
Devel::Peek::Dump(\%DO::);
__END__
SV = RV(0x1c1d05c) at 0x1abf0cc
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x1ab24cc
  SV = PVHV(0x1aadf70) at 0x1ab24cc
    REFCNT = 4
    FLAGS = (SHAREKEYS)
    IV = 2
    NV = 0
    ARRAY = 0x1abb4f0  (0:7, 2:1)
    hash quality = 75.0%
    KEYS = 2
    FILL = 1
    MAX = 7
    RITER = -1
    EITER = 0x0
    NAME = "DO"
    Elt "DO" HASH = 0x95b
    SV = PVGV(0x1aaf3bc) at 0x1abf180
      REFCNT = 2
      FLAGS = (GMG,SMG,MULTI,ASSUMECV,IN_PAD)
      IV = 0
      NV = 0
      MAGIC = 0x1ab0c70
        MG_VIRTUAL = &PL_vtbl_glob
        MG_TYPE = '*'
        MG_OBJ = 0x1abf180
      NAME = "DO"
      NAMELEN = 2
      GvSTASH = 0x1ab24cc    "DO"
      GP = 0x1aaf384
        SV = 0x1c1d748
        REFCNT = 1
        IO = 0x0
        FORM = 0x0  
        AV = 0x0
        HV = 0x0
        CV = 0x1ab252c
        CVGEN = 0x0
        GPFLAGS = 0x0
        LINE = 1
        FILE = "-e"
        FLAGS = 0xe
        EGV = 0x1abf180    "DO"
    Elt "A" HASH = 0x43
    SV = PVGV(0x1abb49c) at 0x1c1d79c
      REFCNT = 2
      FLAGS = (GMG,SMG,MULTI,IN_PAD)
      IV = 0
      NV = 0
      MAGIC = 0x1abb444
        MG_VIRTUAL = &PL_vtbl_glob
        MG_TYPE = '*'
        MG_OBJ = 0x1c1d79c
      NAME = "A"
      NAMELEN = 1
      GvSTASH = 0x1ab24cc    "DO"
      GP = 0x1abb464
        SV = 0x1c1d6f4
        REFCNT = 1
        IO = 0x0
        FORM = 0x0  
        AV = 0x0
        HV = 0x0
        CV = 0x1ab252c
        CVGEN = 0x0
        GPFLAGS = 0x0
        LINE = 1
        FILE = "-e"
        FLAGS = 0xa
        EGV = 0x1c1d79c    "A"
[download]

You can see the CV is identical (0x1ab252c), but EGV is not (EGV = 0x1abf180 "DO" versus EGV = 0x1c1d79c "A"). Soo, wherever pp_caller gets $subroutine from is the wrong spot.

PS - I am not a perl5-porter, so these are guesses.