>>>>> "DB" == Dan Boger <[EMAIL PROTECTED]> writes:
DB> This code was just written to see how things work. I find that
DB> understanding these kind of edge cases helps overall.
In this case, I think you've stumbled across a known bug, so while it
does reveal some implementation details of perl, I'd say the only
lesson to take away for becoming a better Perl programmer is "don't do
that".
Consider the following variation, with the output it gives (on my
system):
use Data::Dumper;
@headers = ("header 1","header 2","header 3");
@body = ("body A","body B","body C");
$h = 4;
foreach (@headers,"",@body) {
print "$h: $_\n";
@body = ();
push @unrelated, "something else " . $h; # <== NEW
push @headers,"header ".$h++;
}
4: header 1
5: header 2
6: header 3
7:
8: something else 4
9: header 4
10: something else 5
With more exploration, you'll probably be able to trigger the
following error out of perldiag (if your perl version is new enough to
have it, otherwise you probably get a segfault):
Use of freed value in iteration
(F) Perhaps you modified the iterated array within the
loop? This error is typically caused by code like the
following:
@a = (3,4);
@a = () for (1,2,@a);
You are not supposed to modify arrays while they are being
iterated over. For speed and efficiency reasons, Perl
internally does not do full reference-counting of iterated
items, hence deleting such an item in the middle of an
iteration causes Perl to see a freed value.
-- Stephen
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