Yes. I think you are right. I also get different results depending upon what has gone on before, but always the same results if the same things have previously happened. So, no matter how many times I run this: 

c:\test>perl -wle"$#a = 10; print \$_ for @a"
SCALAR(0x225138) SCALAR(0x225120) SCALAR(0x225144) SCALAR(0x225168)
SCALAR(0x1824378) SCALAR(0x224f4c) SCALAR(0x2250f0) SCALAR(0x18243cc)
SCALAR(0x18243d8) SCALAR(0x18243e4) SCALAR(0x18243f0)

[download]

I always get those same addresses. The thing I fond confusing is teh way the low and high areans get mixed up.

For example. When I run these two, notice how the first 7 addresses are the same in both, but then the last 3 vary. 

c:\test>perl -wle"@b = 1.. 10; $#a = 10; print \$_ for @a"
Name "main::b" used only once: possible typo at -e line 1.
SCALAR(0x225138) SCALAR(0x225120) SCALAR(0x225144) SCALAR(0x225168)
SCALAR(0x18243b0) SCALAR(0x1824428) SCALAR(0x1824434) SCALAR(0x1824440
+)
SCALAR(0x182beac) SCALAR(0x182beb8) SCALAR(0x182bec4)

c:\test>perl -wle"@b = 1.. 100; $#a = 10; print \$_ for @a"
Name "main::b" used only once: possible typo at -e line 1.
SCALAR(0x225138) SCALAR(0x225120) SCALAR(0x225144) SCALAR(0x225168)
SCALAR(0x18243b0) SCALAR(0x1824428) SCALAR(0x1824434) SCALAR(0x1824440
+)
SCALAR(0x182bd80) SCALAR(0x182bd8c) SCALAR(0x182bd98)

[download]

And if you go on to: 

c:\test>perl -wle"@b = 1.. 1000; $#a = 10; print \$_ for @a"
Name "main::b" used only once: possible typo at -e line 1.
SCALAR(0x225138) SCALAR(0x225120) SCALAR(0x225144) SCALAR(0x225168)
SCALAR(0x18243b0) SCALAR(0x1824428) SCALAR(0x1824434) SCALAR(0x1824440
+)
SCALAR(0x2267c8) SCALAR(0x2267d4) SCALAR(0x2267e0)

[download]

It suddenly starts reusing earlier addresses.

It came up because I was trying to code something that would rely upon the relative address of the items in an array being in ascending order--but that's a guarentee that Perl simply cannot make.

What I really need access to is the (C) array of pointers pointed at by the ARRAY field of the XPVAV, but I would have to drop into XS to get that. Still that might be the only way to do what I am trying to do.

That said, inspiration hit me whilst typing this and I stuck the code is a begin block: 

c:\test>perl -wle"BEGIN{ $#a = 10; print \$_ for @a }"
SCALAR(0x182c120) SCALAR(0x182c114) SCALAR(0x182c12c) SCALAR(0x182c138
+)
SCALAR(0x182c144) SCALAR(0x182c150) SCALAR(0x182c15c) SCALAR(0x182c168
+)
SCALAR(0x182c174) SCALAR(0x182c180) SCALAR(0x182c18c)

[download]

And that seems to produce the effect I am after regardles of what else goes on, provided I ensure that my BEGIN block is run first. Or maybe I should just bite the bullet and code it in Inline::C.

Examine what is said, not who speaks -- Silence betokens consent -- Love the truth but pardon error.
"Science is about questioning the status quo. Questioning authority".
In the absence of evidence, opinion is indistinguishable from prejudice.
"Too many [] have been sedated by an oppressive environment of political correctness and risk aversion."

In reply to Re^2: Internals question. by BrowserUk
in thread Internals question. by BrowserUk

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