Use <code> and </code> to quote your code.

Add use Data::Dumper; to the top of your code, and then add print Dumper(\%hash); before your while loop to investigate what's actually in your hash.

In my example below, everything worked fine.

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};
}
[download]

Output -

$VAR1 = {
          'a' => [
                   1,
                   2,
                   3
                 ],
          'b' => [
                   4,
                   5,
                   6
                 ]
        };
a
b
[download]

By the way, what was the syntax error it complained about?