The implicit use of global $_ in the client code seems a bit odd. This variable is not set explicitly from the command line without careful invocation:

echo myarg | perl -nle 'print "ARG=<$_>\n"'
ARG=<myarg>
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You're better off, at least, fetching from ARGV:

my ($hostname) = @ARGV;
die "usage: $0 hostname" unless $hostname;
my $socket = new IO::Socket::INET ( 
                                  PeerAddr => $hostname, 
                                  PeerPort => '7071', 
                                  Proto => 'tcp', 
                               );
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...or however you want to parse the command line arguments in @ARGV.