After doing a simple test this definitely is the case. If I simply push a string onto an array after deleting the hash key $v ends up getting the string. On my machine the following code prints: 
HASH(0xa00003da0) HASH(0xa00003f38)
HASH(0xa00003da0)
hello

[download]
my $hr1 = {};
my $hr2 = {};
my $hr3 = {"$hr1" => $hr1, "$hr2" => $hr2};
my @values = sort values %$hr3;
print "@values\n";
my (@arr);
foreach my $v (sort values %$hr3) {
  print "$v\n";
  delete $hr3->{$values[1]};
  push @arr, "hello";
}

[download]
This seems very dangerous.

In reply to Re^2: Use of freed value in iteration by Danny
in thread Use of freed value in iteration by js1

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