Anyway, here is what I think your snippet looked like:

while (( $key, $value) = each %hash) {
    print $key, "\n";
    delete $hash{$key}; # this is safe
}
[download]

As of Perl 5.6.1 and later it is considered safe to delete the current hash element obtained from each. However, that behavior wasn't always the case (or at least wasn't always documented to be the case). You also must take care not to arbitrarily delete some other element in the hash while iterating over it except for the most recent one returned by each.

Without seeing the syntax error, I can't say exactly what you're doing wrong. Your code looks ok the way it is.

delete does exactly what you're implying for it to do: it deletes the hash element identified by key, along with its value, which in your case is a reference to an anonymous array.

Note, if you're trying to clear out the entire hash, this is much faster:
%hash = ();
or
undef %hash;

One more observation: You've posted several questions all related to the same general topic. That's great, because most of us enjoy helping. However, it would probably be helpful if you got a Perlmonks account (they're free after all). That would help us to better identify the context of your questions. For me, it was just by recognizing the nature of the question that I knew you were the same person, and that the questions were related, and thus found myself able to provide a more suitable answer. But if you had posted them all from the same user name (other than Anonymous Monk) it would have been easier to make guesses as to the context; I could just look at a list of the last few posts you made. This would help you to get better answers, especially when the questions get more complicated. ...just a thought... ;)

Update: Camel II (which came out way before 5.6.1) says it's safe to delete keys while using each to iterate over a hash. Apparently it's been safe for awhile. It's still a very good idea to only delete the most recent element that each handed you.

use Data::Dumper;

$hash{a} = [ 1, 2, 3 ];
$hash{b} = [ 4, 5, 6 ];

print Dumper(\%hash);

while (($key, $value) = each %hash) {
    print $key, "\n";
    delete $hash{$key};
}
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$VAR1 = {
          'a' => [
                   1,
                   2,
                   3
                 ],
          'b' => [
                   4,
                   5,
                   6
                 ]
        };
a
b
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