1:  sub numtoname {
2:      local ($_) = @_;
3:      unless (defined $numtoname{$_}) {
4:          my (@a) = gethostbyaddr(pack('C4', split(/\./)),2);
5:          $numtoname{$_} = @a > 0 ? $a[0] : $_;
6:      }
7:      return $numtoname{$_};
8:  }

##</code><code>##

foreach (1 .. 3) {
    foo($_ + 1);
    print "$_\n";
}
                                                                                
sub foo {
    $_ = shift;
    $_ += 7;
}


##</code><code>##

sub numtoname {
    my $address = shift;
    unless (defined $numtoname{$address}) {
        my (@a) = gethostbyaddr(pack('C4', split(/\./, $address)),2);
        $numtoname{$address} = @a > 0 ? $a[0] : $address;
    }
    return $numtoname{$address};
}