#!/usr/bin/perl


    use warnings;

    $| = 1;

    $pid = open (SSH,"| ssh user@host");

    if(defined($pid)){
        if(!$pid){
            #child
            while(<>){
                print;
            }
        }else{
            select SSH;
            $| = 1;

            select STDIN;

            #parent
            while(<>){
                print SSH $_;
                while(<SSH>){
                    print;
                }
            }
        close(SSH);
        }
    }

use strict; use warnings;

my $pid = open my $SSH, '-|', 'ssh user@example.com' // die $!;

if ($pid) {
    while( <$SSH> ) {
        print $_;
    }
}
else {
    while( <> ) {
        print $SSH $_;
    }
}

close $SSH or die $!;

use Net::OpenSSH;
my $ssh = Net::OpenSSH->new($host, user => $user, password => $password);
my ($in, $out, $pid) = $ssh->open2($remote_cmd);

use IPC::Open2 qw(open2);
my $pid = open2(my $in, my $out, $ssh_cmd);