Aside from kyle's good suggestions, I think I have an idea as to why you are getting the Invalid argument error.

I did a search on CPAN for Net::Rexec, and after reading the 4-sentence description, I decided to look at the source code (all 27 lines, or so). Here is a snippet:

sub rexec {
    my($host) = shift;
    my($sock) = IO::Socket::INET->new(PeerAddr => $host,
                      PeerPort => 'exec(512)',
                      Proto => 'tcp');
    die "Error opening sock $!" if (!defined($sock));
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It seems that you have to be careful how you pass the IP address to the sub, otherwise it might get corrupted. I think you need to make sure it gets passed as a string, instead of a number (with 3 decimal points). I created a little testcase to illustrate my point:

#!/usr/bin/env perl
use warnings;
use strict;

foo('111.22.33.44');
foo(111.22.33.44);
sub foo {
    my $host = shift;
    print "host=$host\n";
}
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which prints:

host=111.22.33.44
host=o!,
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I do not know why this happens. Perhaps a more knowledgeable monk can explain.

Update: this is my perl version (just in case this is OS- or version-specific):

This is perl, v5.8.5 built for x86_64-linux-thread-multi
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