If you have a complex data structure and iterate over it, I expect refcounting to increase and then decrease the refcount:

C:\>perl -MDevel::Peek -e "$x=[{foo=>1}]; Dump $x; $a=$x->[0]; Dump ($
+a); "
SV = RV(0x1aa4ffc) at 0x1a93898
  REFCNT = 1
  FLAGS = (ROK)
  RV = 0x1a44bac
  SV = PVAV(0x1a45f9c) at 0x1a44bac
    REFCNT = 1
    FLAGS = ()
    IV = 0
    NV = 0
    ARRAY = 0x1a4baac
    FILL = 0
    MAX = 0
    ARYLEN = 0x0
    FLAGS = (REAL)
    Elt No. 0
    SV = RV(0x1aa4ff4) at 0x1a44bb8
      REFCNT = 1
      FLAGS = (ROK)
      RV = 0x1a44a98
      SV = PVHV(0x1a92fec) at 0x1a44a98
        REFCNT = 1                       # <- only one reference
        FLAGS = (SHAREKEYS)
        IV = 1
        NV = 0
        ARRAY = 0x1a4b9b4  (0:7, 1:1)
        hash quality = 100.0%
        KEYS = 1
        FILL = 1
        MAX = 7
        RITER = -1
        EITER = 0x0
        Elt "foo" HASH = 0x238678dd
        SV = IV(0x1a989f0) at 0x1a44b88
          REFCNT = 1
          FLAGS = (IOK,pIOK)
          IV = 1

SV = RV(0x1aa4fd4) at 0x1a938e0
  REFCNT = 1
  FLAGS = (ROK)
  RV = 0x1a44a98
  SV = PVHV(0x1a92fec) at 0x1a44a98
    REFCNT = 2                         # <- now two references
    FLAGS = (SHAREKEYS)
    IV = 1
    NV = 0
    ARRAY = 0x1a4b9b4  (0:7, 1:1)
    hash quality = 100.0%
    KEYS = 1
    FILL = 1
    MAX = 7
    RITER = -1
    EITER = 0x0
    Elt "foo" HASH = 0x238678dd
    SV = IV(0x1a989f0) at 0x1a44b88
      REFCNT = 1
      FLAGS = (IOK,pIOK)
      IV = 1

[download]

I guess you can do clever things with aliases to avoid refcounting (as the stack currently is not refcounted), but it's easy to miss just one of these.

In reply to Re^3: WHY copying does happen (fork) by Corion
in thread WHY copying does happen (fork) by Anonymous Monk

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