Copying? ;-) I don't think anything ends up in @b
Let's analyze the program. First you initialize @a
with some large and small numbers. Then you tie @b -
but to what, one may ask. Well, the result of &^Px$^P. It's not really relevant what &^P returns
(an object - the result of AUTOLOAD), because $^P is essentially 0, leading to &^Px$^P being an empty
string. Hence, it's tied into the class main.
This causes main::TIEARRAY to be called, which is
taken care off by AUTOLOAD - which returns an empty
object blessed into the main class. Now Duff's device copies
the elements of @a into @b one by one. However, since @b is
tied, instead of storing the elements in @b, main::STORE is called. Again, this is taken care
of by AUTOLOAD, but it doesn't store anything, it
just returns another blessed object (which will be discarded
What remains is the two subs. First the empty DESTROY makes
sure destruction of the many objects created doesn't trigger
AUTOLOAD to be called. Then AUTOLOAD. The first line sets
$# to the value %c. This influences the
way how Perl stringifies numbers (basically by doing
sprintf "%c", $number;). It also sets %c,
but that hash is never accessed. Then it prints $_, which, in the case of STORE, contains the
number to be stored. Due to the way stringification has
been altered, it results into garbage on my screen. Perhaps
with another printing device a sensible message appears
(I suspect the numbers in @a not to be random).
And that's it. Nothing is going to be stored in @b.
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