◦ The author doesn't know foreach

In support of which we have, just three lines past the grep statement:

my $i;
 
for ($i=0; $i <= $#a; $i++)
{
    next if _ipcmp($b[$i], $lo) < 0;
    next if _ipcmp($hi, $a[$i]) < 0;
    return 1;
}
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A genuine Perlish for-loop written in C-style. This peculiarity and another grep-loop are found also in cidradd() at line 985. I haven't looked further at the code. OTOH, in the very next function defined after cidrlookup(), cidrvalidate(), we see four kosher Perlish for-loops and a properly (IMHO) used grep, although I must admit there is no guarantee both functions were written by the same programmer. This is doing my nut.