I ran into undefined variables while iterating through a multidimensional hash containing all sort of server info using that function. I silenced them with a simple modification (checking if the parts of the IP is "defined"): 
sub IP_valid {
my $ip = shift;
    $ip =~/^(\d{1,3})\.(\d{1,3})\.(\d{1,3})\.(\d{1,3})$/;
    foreach ($1,$2,$3,$4){
        if ( defined $_ && $_  <256 && $_ >0) {next;}
        return 0;
    }
    return 1;
}

[download]
Sure, that could have been added earlier but that if test was already checking multiple factors so it was easier to add. Thanks for this simple write-up! Just what I was looking for. Wow, 15 years later.

In reply to Re^2: IPv4 regex by flakmagnet
in thread IPv4 regex by ryan

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