use strict;
use warnings;
use IO::Socket::INET;

my ($host, $port) = @ARGV;

my $sock = IO::Socket::INET->new(
    PeerAddr => $host,
    PeerPort => $port,
) or die "cannot open $host:$port";

print $sock <<"...";
POST / HTTP/1.1
Host: $host
Content-Length: -20

a
...

warn <$sock>;