I'm using Net::ARP to do an ARP lookup (using arp_lookup() from the module). For some (unknown to me) reason, when I store IP addresses as keys in a hash before handing them to arp_lookup(), they will not work unless I first assign the key to another variable. I can then use the original hash key in arp_lookup(). It seems odd to me; I've not run into this situation before. I thought at first the module might have Taint checking on, but that does not appear to be the case.

I coded up a simple example demonstrating the (again, to me) oddity. I hope it's just something I'm doing incorrectly. :)

Thank you for any insight into what is happening here.
Casey

UPDATE: I removed the $ipaddr2 assignment I mentioned. Really, any access to the $ipaddr variable between the first arp_lookup() call and second arp_lookup() call will cause the second call to work. So, the print after the first arp_lookup() fills the access role. Thank you, japhy for helping me simplify the example.

Example: 
#!/usr/bin/perl

use warnings;
use strict;

use Net::ARP;

my $device  = q{eth0};
my %ipaddrs = ( q{192.168.1.100} => q{} );

for my $ipaddr (sort keys %ipaddrs) {
    my $mac = q{};

    Net::ARP::arp_lookup($device, $ipaddr, $mac);

    print qq{$ipaddr : $mac\n};

    Net::ARP::arp_lookup($device, $ipaddr, $mac);

    print qq{$ipaddr : $mac\n};
}

[download]

Example Output 
192.168.1.100 :
192.168.1.100 : 01:41:02:8F:70:80

[download]

In reply to Of Net::Arp and Hashes by cmilfo

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