in reply to Update references

Can anyone explain *why* this is happening? I don't know enough of the perl innards to grasp it.

When redefining @a, does Perl actually create a new array at a different memory location, leaving the old existing element simply because a reference still points to it?

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Re^2: Update references
by Eliya (Vicar) on May 13, 2012 at 21:00 UTC

    The reference refers to the scalar retrieved via $a[0], not the array index [0].  The reference knows nothing about the array that scalar came from.  And the scalar will exist as long as its refcount is > 0. 

    $ perl -MDevel::Peek -E'@a=qw(a b c); $r=\$a[0]; Dump $r; @a=(); Dump 
+$r'
SV = IV(0xa95bc0) at 0xa95bd0
  REFCNT = 1
  FLAGS = (ROK)
  RV = 0xa77998
  SV = PV(0xa75c20) at 0xa77998
    REFCNT = 2                   <---
    FLAGS = (POK,pPOK)
    PV = 0xa8ee40 "a"\0
    CUR = 1
    LEN = 16
SV = IV(0xa95bc0) at 0xa95bd0
  REFCNT = 1
  FLAGS = (ROK)
  RV = 0xa77998
  SV = PV(0xa75c20) at 0xa77998
    REFCNT = 1                   <---
    FLAGS = (POK,pPOK)
    PV = 0xa8ee40 "a"\0
    CUR = 1
    LEN = 16

    [download]

    (note the refcounts)

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      That's what I was after, and it makes complete sense. Thanks!

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Re^2: Update references
by Anonymous Monk on May 13, 2012 at 21:00 UTC

    I read in O'Reilly's Intermediate Perl Sec 5.2 that data stays alive until the last reference to it is destroyed.

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