In hv.c is written, that keys (hek-structure) are shared for space optimization. But i don't find any example for that. If i use this hashes $rgb{rot}='aaa ';$cmyk{rot}='aaa'. Is the key 'rot' shared between them? If i look in the output of: 
perl -MDevel::Peek -e '$rgb{rot}="aaa";$cmyk{rot}="aaa";Dump(\%rgb);Du
+mp(\%cmyk)'

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I don't see any shared keys: 
SV = RV(0x1351ba8) at 0x1351b98
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x136ecf0
  SV = PVHV(0x1357fb0) at 0x136ecf0
    REFCNT = 2
    FLAGS = (SHAREKEYS)
    ARRAY = 0x1392a30  (0:7, 1:1)
    hash quality = 100.0%
    KEYS = 1
    FILL = 1
    MAX = 7
    RITER = -1
    EITER = 0x0
    Elt "rot" HASH = 0xaffb6cf6
    SV = PV(0x134fb78) at 0x1351d48
      REFCNT = 1
      FLAGS = (POK,pPOK)
      PV = 0x1369340 "aaa"\0
      CUR = 3
      LEN = 8
SV = RV(0x1351ba8) at 0x1351b98
  REFCNT = 1
  FLAGS = (TEMP,ROK)
  RV = 0x1378990
  SV = PVHV(0x1357fd8) at 0x1378990
    REFCNT = 2
    FLAGS = (SHAREKEYS)
    ARRAY = 0x1368fa0  (0:7, 1:1)
    hash quality = 100.0%
    KEYS = 1
    FILL = 1
    MAX = 7
    RITER = -1
    EITER = 0x0
    Elt "rot" HASH = 0xaffb6cf6
    SV = PV(0x134fc58) at 0x1351f88
      REFCNT = 1
      FLAGS = (POK,pPOK)
      PV = 0x13652c0 "aaa"\0
      CUR = 3
      LEN = 8

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In reply to When will a key shared between two hashes? by gyhor

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