On a modern enough perl you can use the defined-or operator // to use an empty hashref instead. eg:

use strict;
use warnings;

my $result =
{
  '10.4.20.21' => undef
};

for my $mac (values %{(values %$result)[0] // {}}) {
    print "Mac addr: $mac\n";
}

[download]

Of course, if your entire $result is undef then you could easily check for this separately before even hitting the for loop.

In reply to Re^3: Data::Dumper / write output into Mysql by hippo
in thread Data::Dumper / write output into Mysql by steph007

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